I occasionally pick up old hand tools at rummage sales, estate sales, etc. just because I like the look of them, but have found that I enjoy cleaning up and using them too. I have an old cherrywood level that is a decoration in the house, but when I need to hang a shelf or a picture it's very handy to have a perfectly good level hiding in plain sight.

I always thought old hand tools were kind of crap to use though until I cleaned up an old block plane and sharpened the blade. With a sharpened blade it made incredibly satisfying curls of wood on my next woodworking project, where I would have normally used my loud and unpleasant belt sander. I think I get it now why some people really love collecting old tools.