<..."They don't stack, so have to have lots of shelf space.
Imagination running riot, Liz?
I have spent more time than I care to admit in more pubs than I care to recollect, but I have never seen pint glasses "stacked" on shelves in any pub that I have visited.
Waitpersons in the lesser class of establishment may well carry them stacked while transporting them from table to glasswash, but as for storing them stacked ?? Never !