I think it depends on the tool and the condition in which it was found. I have a few old NOS hand planes that were never used. They're only like that once. I'm not going to be the one to degrade their originality by sharpening the iron and running them across some wood, particularly when I have other old planes that are in great "user" condition and will do the same task. I like using old tools, and when I find them in good condition with some patina, and a few bumps and bruises, I keep using them. That being said, I also have a a few "user" quality planes that were inherently fragile from the start. Even though they're not gem mint NOS planes, I use them only sparingly because they're prone to damage/breakage by the very nature of their design, etc.
In recent years, I've been buying older Craftsman tools mostly with the =V= manufacturer's mark on them. Those may have some collector value, however, I buy them strictly as "user" tools to be used. As a matter of fact, I don't mind buying wrenches, sockets, ratchets, etc. with a little age and wear on them because then there's no doubt in my mind that I'm going to use the tool. I'm not going to abuse them, but I will, and do use them. I certainly don't need any of them, so I guess I'm collecting them too, but it's a "working" collection.
Jim C.