This does of course create a secondary risk of businesses laying off older staff in favour of young people and "apprentices", but I haven't seen any clear evidence that this is a widespread problem.
Outside of supermarkets this sort of practice is also pretty entrenched in a lot of small-medium IT businesses: They have a sizeable portion of their workforce as trainees or whatever (they may be underpaid legally, so they almost always are) and don't hire them after their time is up (ever, as a rule). New trainees are then cycled into the slots that are now vacant.
Not uneconomic, but it would impact then in a way that might require reducing profits or flattening wage profiles.
That's not contrary to good management it's contrary to greed.
This was the fear people had.
Somehow most people who were paid less that minimum wage delivered enough value.
Only a few companies needed to stop their service.
Why do "apprentices" deserve less than is considered the minimum living wage.
Even minimum wage has been corrupted.
UBI, or something equally revolutionary, I think will be needed without a major population collapse.