Built-in Blade Bank

Why was it common for older homes to have razor blade slots in the old medicine cabinet with razor blade slot both the medicine cabinets in my house had the slots But the upstairs bathroom which was for the kids had no razor blades in the wall old dear lottery sambad I remember my dad had an old jar, of dead blades, in the bathroom cabinet for years What about just cutting a slot in the back of your

old fashioned slot machine so where do all those used razor blades go? in the bottom of the wall! and they wait there until some poor future remodeler decides to