1. What you consider to be the Bible (presumably OT and NT) contains many so-called “commands” you arbitrarily choose not to obey, e.g. Do not wear clothing woven of two kinds of material. (Leviticus 19:19). So simply because, ” the Bible commands it” [prayer] is not a terribly definitive answer.
2.) Assuming his teachings are authentic (big leap!) Jesus did not believe in germ theory nor in the washing of one’s hands (Matthew 15:11). He believed “devils” caused illness, and magical poles could cure snakebites by gazing upon them (Jn 3:14). So there’s no superseding reason to believe the act of prayer is any more veridical than his other teachings.
In today’s science we know magical incantations, repeated babble and spontaneous prayer have no impact or interaction with physical reality other than perhaps some assuaging psychological benefit for the supplicant. In essence, the only effect prayer has is on the prayerful and no one else.
Science does show that what we call prayer is actually a side-effect of a suite of cognitive mechanisms adapted for other purposes (Dennett).
The human brain is hardwired to engage in imagined one-sided conversations with all manner of inanimate traffic signals, supernatural forces, parents, adversaries, loved ones, phantoms, and even celebrities. As the famous movie line goes (The Sixth Sense): We talk to dead people! (Or at least imaginary ones)
So prayer is nothing more than a ritualized formal agreement to direct primitive neurological processes towards a cherished archetype as a coping mechanism with no empirical evidence of efficacy proven otherwise.