I think personality has something to do with it as well. Some are the “set and forget” types and others the “tinkers”. It can be audio, cars, bikes, whatever. Those of us that are tinkerers, tinker with everything we have. Some one said it above, a direct interaction with our “stuff”. Sometimes, the pursuit is betterment, but other times, it’s just because we can. For those that are the “set and forget” type, I’m jealous. My life would be WAY less expensive!