The US diet did not include vegetables much until relatively recently, and the feeling was clearly that they had to be cooked a long time. My 1930 vintage cookbook has cooking times for 20 minutes for boiling fresh asparagus (and going back to the Roman times, it was known that asparagus should be cooked quickly). Broccoli and Brussel Sprouts took 30 minutes of boiling, carrots 35, corn on the cob 15-25.
Part may have been the variety of vegetables available, which, if you lived in a city, were probably not young and tender.