Welll, originally, ULib wasn't going to change much as a library, and then ULX would be updated/patched as wanted/needed.
So, I believe it was packaged separately for that reason.
However, as a library, while working on ULX, we keep finding things to do in ULX that would better be served as a library function.
Our original intent was for ULib to be used for more (and by more programmers) than just for ULX.
During ULX 3.0 for Gmod10 discussion back in December 2006/January 2007, I believe the idea was suggested to just make a mini-ULib port for ULX, since ULX was more popular. We decided to continue as normal.
Personally, I'm glad we did. UClip, Umotd, UTeam, UccTV and a few other thirdparty addons (sui_scoreboard) wouldn't (have been) be possible if it weren't for ULib as a separate entity.
As for your wondering, though I want to be helpful to those who wish to use ULX, I often find myself thinking "Do I really want this person running a server?"
I then realize that isn't my call, help as much as I have patience for, then stop or hush when I'm at my end.