I've heard it described many ways but its like they return to learn the world 'moved on without them'. Indeed, they are even seen as 'dropouts'. As if they lost their place in the queue/line. I remember one describing the 1st question in job interview back in his home country was "Why did you give up working and just run away to China? Were you just tired of your job?". So you see the thinking! Instead of asking "why did you take on a big new challenge requiring so many new skills?" the local employer saw it as if he'd 'dropped out' and they see the 3 years in China as '3 missing years from your CV/resume'.

Agreed. I reckon this is especially true in Western Europe and the western world in general.

1 year teaching in China you could probably get away with, and an employer may even ask if you know any Chinese, but only really give it a cursory glance on your CV and leave it at that. 2 years or longer and there are going to be problems explaining your prolonged absence from your homeland. The people I used to hang out and party with in my early 20's are now married and settled and have good jobs or their own businesses, as you say, you get out of the "loop".