Answer 1:
with an old forum like running phpbb, it doesn’t matter to the user what the site is running. if it works, it works.
with the fediverse, because it is interacting with other instances in a way forums never even conceived of, it is really important to the end user what software is running. the software is center stage.
Answer 2:
The blossoming of the threadiverse in the past 6 months has prompted/necessitated the creation of a lot of “general purpose” domains.
Your examples are bookclub.phpbulletin.com
and metalheads.vbulletin.net
. But most lemmy instances are not themed around literature or music or anything else. More apt example would have been phpbbtalk.io
or chatvbulletin.xyz
. Such sites did start back in the day. But in the absence of federation they were not likely to cohere. So you don’t remember them, if you ever found them in the first place.
feudalism + capitalism
worst of both worlds