They didn't spar less in the old days. You can read reports of old time training camps tp see the champions and challengers were sparring several rounds several days per week. For several weeks. In Britain many of the professionals in the old days would spend weeks sparring several times a day on the fairgrounds and boxing in small halls two or three times a week. The old gyms above pubs consisted of a few punch bags and a boxing ring. There was a lot of sparring.