Discovering Imgur has its own community and culture is like finding out a group of people live in your closet. You can almost imagine opening the door to grab a coat only to find a dozen people who swear this is the place they bring various outerwear and talk about such things. When you tell them they're in a coat closet, they may get upset and assure you it's more than that, now.
I once discovered a community of people in a PhPBB board I administered - they didn't register on the board itself, but one of the plugins allowed a different type of user registration, and a whole sub-forum itself.
We had no idea, until one day we stumbled into it by accident. It was very much like discovering a family was living in your closet.
Imgur has had its own community for over a decade. This really isn't a good comparison; who stores their coats in someone else's closet and expect for nobody else to interact with it?