I've got no problem doing what God commands. "Because God commands it" is a perfectly acceptable answer for an Arminian or Calvinist in my book. Now a better question might have been, "what does an Arminian or Calvinist hope to gain through prayer?"
"The effective fervent prayer of a righteous man avails much." So I would say yes.
What exactly does it avail? It just increases opportunities, right?
So God is not fair, then, in his dealings with men. He does indeed give some MANY, MANY more chances than others- right?
Many are in hell saying, "Oh WHY didn't someone pray for me more!"
Your prayer REALLY increases the chances of someone being saved.
Your prayer has MUCH to do with whether or not one goes to heaven, right?
Actually in point of fact I don't. I believe God draws all people in terms of the Holy Spirit working on the heart of a man.
So, in your system God chooses to save people based a great deal on the prayers of Christians, right?
He gives some opportunity to all, but he gives a whole lot more opportunity to those who are prayed for.
The chances of heaven increase greatly for that poor soul who is prayed for most and the chances of hell increase TREMENDOUSLY for the one nobody prays for, right?
If that is true, the number one factor that determines whether the merits of Christ are applied to the sinner is the prayer of the saints, right?