I'm not sure you understand the amount of hatred a 14 year old might have against you if you forbid him to have a smartphone.
A case could be made in court that such a restriction is illegal and a form of bad parenting.
That'll teach her to value it (and not lose/smash it like my 15yo mentee keeps doing.) It also means she probably won't have one till she's 16 or so.
Disclaimer: I actually only have a two year old. Maybe I'll change my mind in the next twelve years, who knows.
Besides, being hated by your kids from time to time is part of being a good parent.