Not so much that you’ve missed something or are mistaken, but Reddit is likely promoting those subs because they’re some of the only active high quality (I.e. not bots/astroturfing) ones left.
Not going to go through every example you gave, but the specific sport and team subreddits represent live and ongoing content rather than reposts from a decade ago, with many fans, strong communities, and nowhere else really to go. Consider the decline of traditional, non-steaming live TV networks, where at least here in the US, 98/100 of the top rated events people are still watching the old fashioned way are sports. Same thing.
Not going to go through every example you gave, but the specific sport and team subreddits represent live and ongoing content rather than reposts from a decade ago, with many fans, strong communities, and nowhere else really to go. Consider the decline of traditional, non-steaming live TV networks, where at least here in the US, 98/100 of the top rated events people are still watching the old fashioned way are sports. Same thing.