The thing about alt subs is that you quickly figure out why they're alternatives and not mainstream, and it rarely has anything to do with promotion. I'd add that the very act of promotion changes a small sub into a giant, unwieldy one very quickly.
e.g. Look at anime_titties, the ill-named main alternative to News and Worldnews, and tell me if you can see a problem with that being promoted. I sure can.
for every titties there are 20 other news subs that are just not gaining traction. You only see titties because it's sufficiently differentiated from the news subreddit
e.g. Look at anime_titties, the ill-named main alternative to News and Worldnews, and tell me if you can see a problem with that being promoted. I sure can.