If I want to talk about *some* people in general who want to be X. Is the X should be plural or not? I have this doubt since I remember there's a grammar book explains about this (I couldn't find which book is) and in English, according to the book, this form is used sometimes:

> 
> Plural subject + to be/to have + singular
> 
> 
> 

In the examples below which one is grammatically correct and if there is only one, does the other one still sound natural and is it used in a daily conversation?

1. I don't know why people want to be a teacher.
2. I don't know why people want to be teachers.