Embarrassment at discussions of bugs from 2007 that are still not fixed. (For clarification, I doubt that is really the (main) reason, but longstanding bugs in

Embarrassment at discussions of bugs from 2007 that are still not fixed. (For clarification, I doubt that is really the (main) reason, but longstanding bugs in CAD systems are definitely a thing, and I guarantee there are bugs that old in Inventor (and its main competitor Solidworks), and probably older still ones in AutoCAD).