Have they gone away? Seems most sets still have 18" drums.
They slowy are. For example, the new Tama Starclassic Walnut/Birch comes with a 22x16 in 4-piece config, and 22x14 in 3-piece config.
My slightly old Ludwig Accent CS Custom Elite has a 22x18 and I'd happily trade it for a 22x14. It just takes more space for no good reaon IMHO. Don't want to permanently modify it (there is more to a drum shell design than its length, maybe this one wouldn't sound that good at 14" long), and it's worth too little for me to actually trade it (paid 250$ for the shell kit, but have yet to find another kid under 1k$ that sounds objectively better)
EDIT: Note that I have a 22x9 at my rehearsal space to save on space. Now, that is getting a bit excessive and requires a lot of muffling because the two heads are too close to each other which results in odd resonances. But once muffled and close mic'd... sounds just like a big kick, and probably even easier to place in a live FoH mix.