I think it’s just a sign of people getting lazier and lazier and standards slipping. It’s not the fact they’re wearing pyjamas and slippers as such, it’s the fact they couldn’t be bothered to get into their day clothes.
Another symptom of mindless Britain is people who can’t even be bothered to return their supermarket trolley to the nearest trolley stand, let alone to the store.
In the past, if we saw people wandering around town in their pyjamas, they were usually elderly and confused.