First off; I have a dodgy shoulder so I am one of the first to ask the weight of a bass (9lb+ and my shoulder is shot after a gig). However, in answer to the non-specific question of whether the weight issue is a modern thing... 20+ years ago there was no bass forum on which people discussed/sold/bought basses! I believe it really is that simple; media/communication.
20+ years ago you may have read about the weight of a bass in a magazine and were you the sort who had a dicky back/shoulder/knee/whatever, you'd have given said bass a wide berth and yes I do recall discussing the weight of 70's Fenders with friends, especially as I had a Fender weighing 12lb which likely as not contributed to my knackered shoulder!