The only thing in your entire comment that's not opinion and the only thing worth answering for the rest of the readers.
Despite there no longer being default subs, most of the userbase is still subscribed to default subs. Which drives activity to them. Which causes new users to subscribe to them.
The top 10 subreddits by activity are: askreddit, politics, funny, pics, awww, worldnews, todayilearned, relationship_advice, amitheasshole, memes. 8 of them were defaults. This isn't going to change any time soon as there's a positive feedback loop perpetuating it.
The only thing in your entire comment that's not opinion and the only thing worth answering for the rest of the readers.
Despite there no longer being default subs, most of the userbase is still subscribed to default subs. Which drives activity to them. Which causes new users to subscribe to them.
The top 10 subreddits by activity are: askreddit, politics, funny, pics, awww, worldnews, todayilearned, relationship_advice, amitheasshole, memes. 8 of them were defaults. This isn't going to change any time soon as there's a positive feedback loop perpetuating it.