If you trusted God you would not ask him for something more than once. You would not need to.
But you do repeat prayers.
You may pray persistently for yourself. You may pray persistently for others.
A brief prayer brings you no comfort. Longer prayer might. It is the relaxation that is working on you not the prayer. A brief prayer does not feel like helping.
People in times of tribulation may get a little comfort from a lot of prayer. If prayer helped, then one brief prayer should be enough but it is not. It is a placebo working on them that helps not prayer.
Prayer is impotent when one prayer is not enough. Its failure is a potential proof that there is no God. Yet Jesus strongly censured those who think they will be heard for their many words.
Prayer is immoral for the quality never makes a difference but the quantity might!
If religionists thought that one prayer were enough, they would not be saying more. And if one is enough and God cannot do more than he does then prayer is blasphemously and unreasonably complaining about this. People forget to do it which a good God would not allow if that is all we are put on earth for. Sinners feel like praying so the inclination to prayer is not evidence for the existence of God. Prayer disproves God though it is supposed to be evidence for him.
SO?
Atheists have a right to see prayer as an evil activity. And this attitude need not be a non-religious one for religion itself when looked at closely says just that. Prayer conditions and reinforces conditioning. Prayer conditions people to prefer the rights God allegedly claims and has to human rights and to deepen the religious hold on the world with all the terrible disasters that brings. Prayer insults people for the same reason that saying the famine ended because you lit a gold candle on New Years Day is insulting and superstitious. The view of God that it proposes for us is unacceptable. It has resulted in the hypocrisy that is so common in people of faith. One wonders if praying people who seem undamaged by praying really believe or only imagine that they believe.
The benefits of prayer do not come from prayer at all which is why we should oppose faith in prayer and have no regrets. The benefits are nothing compared to the damage that is done. Destroy regard for prayer even if only for the sake of principle. The vulnerable are the ones who need our concern - not those who pray.