I suspect there's a number of issues.
First and foremost, the size of the os may itself be part of the problem. My first OS was a small group while both of the "cold fish" ones are both large -- 2-3X bigger. Smaller groups, I believe, take notice of new comers more quickly and are more likely to actively engage new folks in conversation. In a large OS, it is easier for new people to be overlooked and ignored -- both accidently and not. In talking to a few other folks from other OS's I've met at shows, this seems to be a very common phenomenon.
Another difference -- my old os was mainly comprised of folks growing on their window sills or other small grow areas. Very few had greenhouses. The two 'unfriendies', however, were heavily weighted toward greenhouse growers. (Not that I'm trying to knock any of our greenhouse folks here! ) So when show-and-tell time at an OS meeting comes around or plants are needed for shows, small homey OSs appreciate the plants that other home hobbyists are able to grow and need to get as many members involved as possible at showtime to put on a decent display. Greenhouse heavy OSs are more likely to be used to seeing large specimen-sized plants and, for those who have had a greenhouse for many years, to have lost sight of the challenges a small grow area hobbist faces and hence lack appreciation for the small growers triumphs. Whether such an attitude, where it exists, is snobbery or just thoughtlessness could be argued either way.
The 'oldtimers' factor you mentioned, Bill, I think may also play a role if those follks are the no nonsense types. Some of the oldtimers I have met are terribly serious about orchid discussions. By 'serious' I mean that they don't seem to have time or patience for light-hearted discussions on orchids or even idle chitchat at an OS meeting -- they're pretty much 'all business'. If an OS is predominantly made up of such folks, that OS can very well come across as 'unfriendly'. In contrast, 'oldtimers' who have a more light outlook, can be a great fount of help and information.