I thought you were implying it's a failing of grouchy employees ('refuse to adapt') - I just think that might be sometimes hypocritical as companies love to talk about their culture etc., if you change what that is (and previously talked about it) then you should expect some negative reaction to it, and if you don't (or talk about how you're keeping it the same) then it seems unfair to criticise someone saying it's changed or not liking that.
(Personally I think I'd rather companies uncultured/not talking about it, but if they do it should make sense and be consistent with actions.)
I was replying to the point where OP says companies end up hiring externally when they grow and need new layers/functions.
Most of the time (in my experience), it's not that employees want to take those new jobs but upper management fails to promote them and more that the company is becoming something they don't like (which makes sense, otherwise they wouldn't have joined a startup if they prefer big corps)... and they don't want to adapt.
It's all perfectly fine, IMHO. People move on. Companies move on. Some people will adapt (because they like the new reality, or they need to like it, or..) and others won't. And by adapting I'm not saying become "better" but different only.
I think the worst case is when both parties don't realize it and don't take action. Then you get upper management hiring externally, saying the employees that helped the company grow are bad employees, etc. And the initial employees saying upper management is clueless, sold out, lost their way, betrayed the culture, etc.
