Sorry old chum - that seat's taken

Is it just coincidence, or is space bagging a predominantly middle-class characteristic?

It always seems to be those who look particularly comfortably off who are adept at it.  I'm thinking of the man who bags (literally, by scattering luggage around) all four table seats in a crowded train compartment.  Or the woman in a busy local  coffee place on Saturday, who was sitting alone in a prime position with coat on one chair and bag on another.

On this occasion, I decided to confront.  

"May I sit here?" I ventured, boldly.  

"Ye-ess", she said drawled, doubtfully.

"It's just that there is a bag on this chair....."

"Yes - it's mine."  

And then silence, with no attempt to move it.

Perhaps it's a public school thing:  a mixture of self-confidence and bloody-mindedness in respect of others.