Ath'kethin
Elder Thing
As a longtime gamer (30-ish years) running DCC exclusively for about three years now, I have to say that your statement matches my experience. Many people love starting play with a character that's fully developed and established, but lots of us - and it isn't just old timers IME - like starting a character full of potential and seeing how it goes.DCC popularized that, but I don't think that is why most people want 0 level characters. They want 0 level characters in order to play the "zero to hero" story that D&D used to provide out of the box.
The level 0 concept, especially in DCC RAW, requires ceding a LOT of control to the dice. That approach certainly isn't for everyone, but it makes for a certain kind of story that still holds a great deal of appeal. The most common response I get from 5e players coming to my DCC campaigns is relief, in a very "oh my gods, this is so much easier" sort of vein. Not all of them feel it's worth the experience, but a lot of them do.