SDCC is a different animal. Yes, it's a lottery, but a lot of people go back year after year. It's almost like VIG in that they have a preregistration where only people who attended the previous year are eligible to participate. They sell about half of the tickets during preregistration, so even if everyone wanted to go year after year you have a 50% chance. Since not everyone returns, your odds are something better than 50%. And then if you don't get a ticket in preregistration, you can try again in open registration. Yes, there your odds are smaller. They don't publish any stats, but anecdotally it seems to be in the range of 10% to 20%. But getting tickets can't be impossible or you wouldn't have people able to attend ten years or longer in a row. I know many.
And yes, everything there is an insanely long line, but holding spots in line is acceptable. One person can hold a spot in line for 3 more people. So people take shifts. With SDCC it is an absolute must to travel with a group or make friends with a group. There are ticket buying groups, line groups, hotel registration groups, etc. Try it solo and you will miss a lot. In the end, it's fun, but its not for everyone.
I'm not sure if I see Gen Con going down this path.
As much as people here may dislike hotel registration for Gen Con, it's ten times worse for SDCC.