I think the biggest problem comes from the guys who have the big egos about their average on a house shot, not necessarily about people who simply have a big average on a THS. They are only familiar with a THS, and don't have the experience to realize what's going on or be objective about it. They're used to being successful on the conditions they bowl on, and that equates as being good or proficient across the board to them. So when they finally encounter something they don't have success on, whether or not they actually realize they aren't as "good" as they thought they were, the reaction usually isn't that, it's usually to blame the lanes, equipment, etc. The rest of us don't like that, and so there's a general disdain for nearly everyone who has a high average on a house shot. Being "good" is also all about perspective. 30 years ago, if you averaged 205, you may not be pro material, but you were pretty darn good, and I'd consider 205 on a PBAX league fairly good too. Take a 240 average on a THS and put him on a PBAX league, if he finishes with 205, that's still pretty respectable in my book, but he may not see it that way.
It's simply that they don't understand or are inexperienced, and speaking from my own prior inexperienced opinion when I first started getting into tougher shots, if you tell someone ELSE who doesn't understand, "Oh I went to this tournament and averaged 200" when you average 225 on a house shot, you know how they're going to react. They're going to razz you for it, or give you grief, or comment on how terrible it went for you, even if you were to say you won! Because the other people would then assume you had no competition, or that there was something wrong with the lane machine and completely write it off. People associate skill with score, and NOT score in relation to scoring pace. People will always see a 230 average in the midst of several other 230 averages as better than a 205 average leading a PBAX league.