For a lot of people a visible crease isn't a big deal. For some people it is a big deal. Luckily Apple will sell multiple different iPhone models.
As mentioned right in my post, they are sold in the millions. Not hundreds of millions, but millions. However, this includes both flip phone styles and the mini-tablet styles. I suspect a lot of people here would love to buy a iPhone flip phone. These are 3-4" folded but 6"+ unfolded.
BTW, I've mentioned this before elsewhere, but Samsung puts tons of foldable phone product placement into K-dramas these days. It's almost become a trope to see a character aggressively close their Samsung flip phone to hang up on someone. 🤪