Emulators suffer from bitrot just like the software they're emulating. I've seen several fall into disrepair in recent years -- eventually we'll lose the people that remember how the the old systems worked. Centralizing the development and publishing it on the web seems a good way to keep the preservation effort humming.

(And as pointed out in the OP, getting something like Trumpet Winsock to work against a 21st century internet is non-trivial)