Which is a really good thing, IMO.
I’m upgrading from a 12 to a 15 because of USB-C and the other improvements that have accumulated, and after that I’m leaving it alone for a long time.
If USB-C wasn’t there, I wouldn’t even bother as my 12 works perfectly fine, Safari feels snappy and this phone could last a good long while still.
Pretty much what the other poster says, plus the fact that there are other improvements that weren’t big enough to upgrade before, but USB-C tipped the scales.