It is more difficult to save now because of the rental market, the changing nature of employment and yes, changes in expectations.
The first two are probably bigger factors. But DH is older than me, just retired, and friends older than him were starting their families and paying that 15% in the 1970s. These were successful young lecturers and postdocs then. I listen to them recall ‘the old days’.
Usually the wife was home with young DC, because no child care. No car or maybe an old banger, no central heat, no dishwasher, no shower, no tumble dryer. DC clothes from Oxfam. A decent dress from M&S was a treat. Basic, cheap home cooked food, lots of home sewing, hand me down toys, etc. Camping holidays only. What’s a restaurant?
You can’t live that way with two employed parents in the family and I am not suggesting it is virtuous, but that was normal life for young academics 50+ years ago. Now it would feel too deprived. So yes, our expectations have changed.
Progress and improved standards are good. I agree that greedy employers and landlords are bad! But the feeling by many on this thread that life is harder now seems to be to be largely a result of these greedy actors.