Because people didn’t dress up as mermaids and go to cons and express how deep down inside they truly are a mermaid, and have a high likelihood of fucking someone else who also felt the same way.
Not all furries believe themselves to be or want to be animals. It’s a simple interest in anthropomorphic animal art. You’re thinking of therians.
I don’t think many people had “a thing” for mermaids though. It was just another human creature with boobs. I don’t think most people thought about it any deeper than that
Uh… I hate to tell you this but people absolutely dress as mermaids and do conventions… There’s a whole home industry of people who make custom silicon tails.
Dunno what to tell yeh mate, it’s about as oldif not older than Furry culture. Weeki Watchee springs started a whole thing with their Mermaid shows and the subculture basically took off from like the early 60’s… And was probably about as horny as a lot of other subcultures that started around the same time.
