I think the main issue is we don’t know where Lemmy is one year from now. I have already started to see a decline in my usage because there simply isn’t enough content. /c/football is virtually dead it feels like and it (or rather /r/soccer) was my number one subreddit.
I think you’re spot on and it applies in general to why we see a trend of subscriptions. When we all got our first smartphones, most apps were local and it didn’t cost the developer more if they had 1M downloads compared to if they had 50 downloads.