Why did they lay hands on people to receive the Holy Spirit?
In most (but not all) cases in the New Testament, once a new believer had been baptised in water, someone would lay their hands on them immediately and pray for them to receive the Holy Spirit. The person praying and laying their hands upon a new believer is not the one who causes them to receive the Holy Spirit. The only one who does that is Jesus Himself. Jesus is the one who baptises us in the Holy Spirit. We learn this from John the Baptist:
6John was clothed with camel's hair and wore a leather belt around his waist, and his diet was locusts and wild honey. 7And he was preaching, and saying, "After me One is coming who is mightier than I, and I am not fit to stoop down and untie the thong of His sandals. 8"I baptized you with water; but He will baptize you with the Holy Spirit." Mark 1:6-8 (NASB)
29The next day he saw Jesus coming to him and said, "Behold, the Lamb of God who takes away the sin of the world! 30"This is He on behalf of whom I said, 'After me comes a Man who has a higher rank than I, for He existed before me.' 31"I did not recognize Him, but so that He might be manifested to Israel, I came baptizing in water."
32John testified saying, "I have seen the Spirit descending as a dove out of heaven, and He remained upon Him. 33"I did not recognize Him, but He who sent me to baptize in water said to me, 'He upon whom you see the Spirit descending and remaining upon Him, this is the One who baptizes in the Holy Spirit.' 34"I myself have seen, and have testified that this is the Son of God." John 1:29-34 (NASB)
So then, if Jesus Christ Himself is the One who gives the Holy Spirit to us, or baptises us in the Holy Spirit, what is the role of the person who prays for us and lays hands upon us? They are, at most, a helper. They can guide and advise us. However, they are not the source, or the giver, of the baptism in the Holy Spirit. That is Jesus alone. The person who prays for us and lays hands upon us merely helps us to receive the Holy Spirit. They show us what to do and what to ask for and they help us to ask.
We are not dependent upon that person. We can receive the Holy Spirit without such a person's help. Remember Cornelius in Acts chapter 10. He, and those around him, received the Holy Spirit while they were just listening to apostle Peter preaching. Nobody laid hands on any of them, or even prayed for them.
You do not necessarily have to have the help of any person to receive the Holy Spirit. You can be alone if necessary.
That should encourage you to be confident that you will receive the Holy Spirit if you ask, even if you have no fellow believer who is able and willing to pray for you and lay their hands on you. Human help and support is useful, but not essential. You can receive the Holy Spirit even when you are on your own, just as I did (see below).
Therefore, we benefit from a fellow believer praying with us and laying hands upon us to ask Jesus to baptise us in the Holy Spirit. That is the normal, biblical model which we should follow. However, it does not have to be done that way. Jesus can baptise you in the Holy Spirit even if you are alone, with nobody to pray for you or lay hands on you. It can happen even if nobody in your church understands any of this, and even if they actively oppose it.
No man can deny you the freedom to receive the Holy Spirit from Jesus. It may be that there is nobody willing or able to help you, or that nobody in your church believes in this. However, if they say it is not for today, you can simply ask God the Father and the Lord Jesus yourself, directly. Jesus will be glad to do this for you. It is His wish, and the Father's wish, that every one of His disciples should receive the Holy Spirit. Therefore, He will not deny you when you ask:
11"Now suppose one of you fathers is asked by his son for a fish; he will not give him a snake instead of a fish, will he? 12"Or if he is asked for an egg, he will not give him a scorpion, will he? 13" If you then, being evil, know how to give good gifts to your children, how much more will your heavenly Father give the Holy Spirit to those who ask Him?" Luke 11:11-13 (NASB)
It is interesting that in this verse we are told by Jesus to ask God the Father to give us the Holy Spirit. So, although Jesus is the one who actually baptises us in the Holy Spirit, we can, and should, ask the Father. He will then answer that prayer through His Son, Jesus Christ. This is an illustration of how the Father, Son and Holy Spirit work together in perfect cooperation.
So, to reiterate, if you are alone, with nobody suitable or willing to help you, or pray with you, do not feel thwarted or discouraged. Just ask God the Father and the Lord Jesus Christ directly, for yourself. Then believe that your own prayer will be answered. I will cover this more fully below.
Note also from the above passage from Luke 11 that we can be confident that if we sincerely ask God to give us the Holy Spirit then He is the One whom we will receive, not a demonic counterfeit. If we pray sincerely then God will never give us something bad. Neither will He allow the Devil to give us something false instead of the Holy Spirit. In other words, if we genuinely ask God for the Holy Spirit, then He will not allow any demon to give us something false instead.
If a human father can be trusted not to give his child a scorpion when he asks for an egg, then how much more can God be trusted? Therefore if you are a genuine believer, and are sincerely seeking to receive the Holy Spirit, do not fear that you will receive anything false. Go ahead and ask to receive the Holy Spirit with confidence. However, I would stress again the need for you to be genuine and sincere.
However, it has to be said that there is a danger. If we allow another person to lay hands on us, we could receive a demonic spirit if that is what they have. In other words, if they themselves are not genuine and are operating in an unbiblical way, with false teaching, a carnal lifestyle, and false spiritual manifestations, then they could pass on to you what they have.
Therefore examine the "fruit" that comes from their lives. Also test the accuracy of their doctrine closely before you allow anybody to lay hands on you to receive the Holy Spirit. If there is any doubt about that person, you can simply pray by and for yourself.