Yes, there’s been plenty of discussion here about it.
Here’s one about external core being enabled at TiddlyHost:
… and this more extensive discussion:
The benefit for me (for example) is that we avoid the redundancy of hosting my core for each of my tiddlywiki projects, and I (and my students!) avoid the download bandwidth burden of downloading that core each time (beyond the first) that one of my tiddlyhost projects is loaded.