Well Jesus says that we should not. (Mat 6:6 NIV) But when you pray, go into your room, close the door and pray to your Father, who is unseen. Then your Father, who sees what is done in secret, will reward you. It is a command that is not obeyed by anyone.
We read accounts in the Bible where Jesus told someone not to do something, such as the leprous man in Mark (1:40-45) and they did it anyway. We say to ourselves that we would not do something that Jesus forbid and yet we pray in public.
We are told what the results were when the man that was healed disobeyed Jesus. It didn’t hurt the man, but it did impede the mission of Jesus. (As a result, Jesus could no longer enter a town openly but stayed outside in lonely places.)
It seems to me that praying in public has the same result. It doesn’t hurt us, but it can impede the “Great Commission”.
Suppose someone who is not a believer visits a Church and the congregation prays for the healing of someone. The unbeliever doesn’t have any faith in God. He doesn’t realize that God is in control and that God might not grant the congregation’s request. If he comes again the next Sunday he may think that if God will not grant the passionate prayers of the whole congregation then there is no God, or no God that he wants anything to do with.
I have a hard time praying about anyone’s health, even in private. I do because I do not like it when anyone suffers (especially me), however it might be God’s will. I know that God knows everything, so God knows who is sick. He doesn’t need me to tell Him.
Every time I pray about someone’s healing I remember the account of Hezekiah. When God told him it was time to die he threw a fit and prayed that God would not take his life and God granted his request. Hezekiah was a good example until he did not accept the will of God, but after that he sinned greatly. God sometimes grants requests that are not in His will so be careful what you ask for.
I view prayer as a private conversation between me and God. It is only what I have to say to Him as He has said everything to me that He wants me to know, through the Bible.
I do not include praise and thanks as prayer. I believe God should be praised and thanked in public and that is the only kind of prayer (if you consider it as prayer) that should be public.
I’m not trying to make waves, I am only trying to explain my understanding of why Jesus said do not pray in public.