What was the intention behind self serve? Prevent theft?
I assume you mean 'full serve' LOL, as 'self serve' is what we have now..........
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Mainly a hold over from the prohibition era I suspect.............( I wasn't born when they started this, or for most of its existence).
But also, it wasn't an uncommon way to do retail back-in-the-day.
I remember Consumers Distributing, which was a similar format, come in, peruse the catalog, write down your preferred item number(s) on a slip of paper, hand it to a clerk who goes and fetches it.
Aside from it being that way because it was.................there was (and is) a certain advantage in this format; space efficiency. The way in which you store goods when the public doesn't require access is different than when they do.
Also, no 'pretty displays'.
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Worth noting, that's how grocery stores used to be too (they were much, much smaller).........No, I don't remember that personally, LOL..........
Here's a story on how the change towards how we do things now happened:
www.tvo.org
The LCBO just took another 55 years to catch up.