it does if you want your buttons to be anything close to the size of your finger, or if you want the text to be readable (which is adjustable, but most people do not)
we can't have small phones because the os design can only be so flexible before it starts either being crap at every size or having so many edge cases that internally it's stupid complex.
having limited sizes means the sizes they do have can be well covered
i haven't used Google for search in years. duck duck go ftw