Because they think that someone is being paid to pick it up, so why should they (a) do their job for them and (b) do it without being paid.
I guess it's a variation on the old upper-crust belief that the nobs are pretty much obliged to throw their clothes on the floor because "that's what the servants are for".
Good Morning Saturday 25th July 2026
What’s a household item that reminds you of your grandma’s house?
