When and why did this start happening on shirts?

I expect to be able to push the cuff back to see my watch and know what the time is. This often not possible now unless the watch is slim. I also expect a cuff to accommodate a larger - but not enormous - watch.

Neck issues can be explained by weight gain and shrinkage but, even if you balloon to El Fat Bastardo size, you do not normally gain weight on your wrists. Unless you are a darts player like Andy the Viking Fordham and he normally wears half sleeve shirts:-
http://www.telegraph.co.uk/sport/othersports/darts/6319141/Andy-The-Viking-Fordhams-autobiography-hits-the-bulls-eye.html