There are other posts like that. Just search for Inform vs TADS or something.
There are various reasons why people adopt certain platform. ScottKit isn’t for everybody, but I like it very much! As far as Inform vs TADS, I think it’s because Inform is good enough, and whenever people run into problem, questions are answered quickly and well. Good support overall.
The fact is, most people’s introduction to IF is via Infocom/Inform games, and naturally gravitate toward such systems. Without a good reason to move to other platforms, people simply stay with Inform.
Bob Bates did have a good reason, and wrote his game in TADS. YMMV.