I don't know, I think that a "hobby" should be linked to use or an activity, specifically, not simply ownership. Consumerism for the endorphins isn't really a 'hobby', it's an addiction at best (and I have some personal experience in this area).

If you're renting or leasing cars for a specific use, like racing or camping, I think that's completely defensible; I even think certain vehicles like RVs should probably mainly be rented or leased, to make sense.

But "having the newest car for my ego" isn't a 'hobby' without diluting the meaning to nothingness.