They are doing it everywhere. At the cinema, on the tube, at the tennis, in the dentists' waiting room. It's not just the legs - it's the arms too.
I am a smallish woman and I understand that a bigger person takes up more room than me, and that men are mostly larger than me. Is it all that junk between their legs that makes them do it? Is it the broader chest that says "I need to spread my elbows over both the arms of this chair and invade your space". Do large breasted women do it too? (I've not noticed - 30E cup here, so wouldn't understand.)
Or is it "I AM A MAN AND SOOOOOO MUCH MORE IMPORTANT THAN EVERYONE ELSE IN THE WORLD"?
So AIBU to think that they could be a bit less entitled?