I think it depends a lot on the style and size of pants, and it's just a personal preference.

While I prefer smaller phones for how they feel in the hand, all of my pants could easily fit a phone 7" or larger. But if normal phones don't fit in your pockets, then a folding phone makes sense.

Also personally I'm the sort of person who dislikes how bulky traditional wallets are, and I'm bothered by my earbuds case. But point taken that a folding phone still isn't very thick generally.