But the old "flat above a shop" used to be a pretty nice place to be, i.e. easy access to the shopping street, and the shop underneath probably opened "normal" daytime hours, closed on Sundays, etc. I lived above a shop myself for many years, it was a newsagents, and it was completely fine - bedroom at the back so not awaken by the vans delivering the papers at 5am!
Nowadays, heaven knows what you'll be above, probably either a greasy smelly fast food place, or a money laundering barber shop/nail bar/ethnic convenience store, open all hours, early to late, 7 days per week, lots of which are a magnet for anti social behaviour from the local yobs and drug dealers who hang out close to shops these days.
Completely different as the "High Street" has changed beyond recognition. Another aspect where things have changed.
As for the "stepping stone" aspect, I think a lot of that is the sheer cost of moving these days, i.e. stamp duty, legals, surveyors, mortgage fees, removal firms, which make moving very costly, so people do tend to hold back a while and buy later in the hope of having to move fewer times in the future. Another aspect is the shortage of "starter homes" which seem to be snapped up by BTL landlords these days to increase their portfolios, meaning first time buyers are often ignored by estate agents as they already have "known" landlords on their books who they know will find it quicker/easier to buy as they have funds in place rather than be delayed by banks doing all kinds of checks on first time buyers.