Funny to think of W95 like some kind of luxury that a shopkeeper has to keep teenagers out, as if you were trying to test drive a Mercedes, or trying out guitars like that scene from Wayne's World (1992)
i'd hand over one of those novelty Bill Gates dollars to show the shopkeeper i'm serious
Or maybe the PC was in the back of the shop, in some non-public area that a bunch of random, inquisitive people (regardless of age) weren't welcome to visit.
Maybe the area was just trashed or otherwise unseemly, and would leave a bad impression. Maybe the shopkeeper smoked weed back there and didn't want to expose kids to Bertha, his prized six-foot bong. Who knows.
When I've worked in shops that sold electronics with a retail storefront, we tried to keep the showroom looking very nice and uncluttered. The back rooms where we repaired stuff and tinkered around with gear were very different: These were utilitarian spaces that regular customers weren't often invited to see.
Nothing particularly untoward ever went on back there, but still: There's reasons why shops (of all sizes) have interior walls. :)