At what age do you think a child should be expected to say "please" when they want something?

So I have a 14 month old here. She has a vocabulary of about 50 words and understands many more even if she can’t say them. She can say many of them upon request. She’ll nod “yes” or shake her head “no” if you ask if she wants something.
I think she’s old enough to learn “please” even if she doesn’t know why she has to say it, but her mother doesn’t think so. She said we need to wait until she’s older because she doesn’t understand what it means.
I mean, I’ll do whatever Mom wants, but what are your thoughts on this?