Mmm, a believer might say that the difference is how much effort you're expending, on the theory that, if it's too easy, you don't deserve help. It's not a magic spell, it's an appeal to God's mercy, begging him to intervene for you. If you don't take it seriously, why should he?

Although I suppose there might be religions that believe that the purpose of prayer is to ensure that the gods have lots of prayers to listen to, like a celestial iPod. For them, a prayer machine would make plenty of sense.