Security guard explains why it's called a unicycle

I was riding with beull today and an older security guard (70s?) comes up to us. At first I thought he was going to give us a hard time about riding in the parking lot, or something along those lines. He comes up and says “I use to ride one of those 50 years ago.” We exchanged small talk and his line to us was “Do you know why they’re called unicycles?”
Our reply: “yeah, because they have one wheel.”
Him: “No because they’re useless cycles.”
Weird old men…

That was rather pissy of him. But it does sound like something an old man would say. Not quite a pun, but he tried.
-David Kaplan