MC DOES try and tell her, though he doesn't tell her the details. The official walkthrough from DPC even notes "This decision has major consequences for Maya!" even though, to date, there are no consequences in the game.Correct me if i'm wrong but isn't her "menu" optional? So for those who ignored it, it wouldn't make sense to make a big deal of this because they don't know enough.
I said this earlier but I can imagine a situation where a MC who declined to take Quinn's service can't convince Maya of the truth, and you need to have accepted her number and not ordered all the options to be able to set up a situation where you place an order and show Maya that one of the girls shows up.