That's just because the legal options were easily available, right? Kind of like people stopped pirating as much when Netflix was actually decent. But now the tides are turning again, so maybe the fan subs will start coming back as well.
Still, though, I wonder if that mindset is still going to be around.
I remember seeing (I think Netflix release) of Komi-san can't communicate, noticing A lot of things being missed, like Komi's literal main manner of communication (A notebook where she writes) not getting any translation for some episodes, or a lot of things I'd have to fill others in that normally at least would have been a T/N in fansub
It was bad enough that I went looking elsewhere to see if I had missed more than I realized, and the fansub did have everything covered
Here's the answer right here...
* Shonen anime, which are consistently the most popular ones, are also on netflix and probably several other services. Eg, demon slayer, dandadan, etc.
* there are still shows that are japan-exclusive because nobody bothers to license them. Roboshinkalion is an entire franchise that nobody cares to import! We actually had to wait two extra years for gridman universe because nobody bothered to license it for English localization!
* just this year they failed to obtain the rights to Mobile Suit Gundam G-Quuuuuux and Panty and Stocking With Garterbelt because amazon outbid them. These are both new entries in well-established brands and they're both made by studios with large fan followings (khara for g-quuuuuux and trigger for panty and stocking).
* somehow Hulu ended up breaking harmony gold's 45-year blockade around the macross franchise and won exclusive streaming rights.
* netflix has a lot of exclusives these days, including Jojo stone ocean and the upcoming steelball run.
Outside of Asia, Crunchyroll is a de-facto monopoly on legal anime. From the article, 70% of new releases are exclusive to Crunchyroll. They're not losing customers to platforms with better subs, because customers have no alternative.
(Besides pirating, but I assume the golden age of Tier 1 fan subs is over)