A valid point, but nonetheless owning a second pair of ear buds is not a high bar. Ear buds are sold by nearly every corner gas station, grocery store, and 711. Typically for <$20 regardless of region.
The primary issue is interchangeability. In the event you leave your earbuds at home. Borrowing a friend's, or purchasing an additional set is a simple. This is nolonger a simple solution.
Except it's still a simple solution for two reasons: 1) if you get the phone you get an adapter to let you use all 3.5mm headphones 2) many many many other people will have the same phone, so you'll be able to borrow their headphones.
The primary issue is interchangeability. In the event you leave your earbuds at home. Borrowing a friend's, or purchasing an additional set is a simple. This is nolonger a simple solution.