They're the cheapest, or close to it, though they make it up with all kinds of other tricks. I think it's really just that simple for a lot of people who don't know or don't care about all the other stuff.
Sure, we know about them, but other people are looking for the lowest price they can find on a search for 'cheap domain registration'.
True. I guess what I'm trying to say is that I'm surprised how many technically knowledgeable people used them. This site is full of people talking about moving away. Wikimedia used them! I can see why Joe Random would, but it makes no sense to me that someone who knows what they're doing would.
Sure, we know about them, but other people are looking for the lowest price they can find on a search for 'cheap domain registration'.