[conception]

There are two things that really scratch the dopamine itch at the table that I think plays well to DnD - 1) the d20. 5% of something amazing or terrible happening is just the right amount of chance for things being regular but not expected. And it being a single lotto ticket somehow makes it better.

2) fistful of dice - eventually you get to toss a fistful of dice and its very satisfying to climb that ladder.

DnD has both and that combined with ability progression I think really locks people in to the system, even outside of the network effect of it. GURPS for instance is great but 3d6 and getting an 18 just isn’t the same, for instance.