In my experience, they do because of the sort of players they attract and the engagement required of them.

Complicated games with many source books attract rules lawyers, who dominate the group experience by way of using their knowledge of obscure rules to control the play.

Whereas overly simple games, like FATE, lack enough structure to guide more timid players through the experience, and so play becomes dominated by the prominent story tellers in the party.

Play "Warhammer Fantasy Role Play" and get back to me. How many fingers did your players have by the end?

Or Dungeon Crawl Classics.. How many level-0s made it through the meat grinder?

The randomness in other system leads to some interesting developments that you don't see in D&D. There's also the culture of the games. In modern D&D there's almost a contract between the players and DM that the players aren't to interfere with the DM's world building and the DM will not interfere with the grand destinies of the characters.

It's completely uninteresting to me. I want to play and play with as many different characters as possible so I can see different parts of the system and worlds. Playing the same characters from level 1 to godhood is dull. Character death should be frequent and glorious.

I also like Blood Bowl so.. I have a pretty high tolerance for nonsensical, dice driven, narratives. There are so many good story hooks if you just go with it.

Wargame systems where combat is the focus and fudging is cheating tend to use more small dice so you end up closer to a normal distribution of values, rather than a uniform distribution. That avoids stuff that doesn't make sense like a shepherd rolling repeated natural 20s while a dragon rolls 1s - if the dragon is rolling 5 dice for an attack the floor of that is still above the shepherd's ability to defend.

Damn, have I got, like, 20 years of blogs, 40 years of forum and BBS posts, and 60 more years of magazine, zine, and rambling manifesto articles for you.