Many of the stuff I have is there just because I can't rent it when I have a bit of time to use it.
What a loss to our communities as online retail drives them out of business. If I can get my supplies from Amazon for 20% less, but then have to buy the tool that I could have borrowed from the local store, and spend twice as long doing the job because I didn't talk it over with the experienced guy behind the counter, have I really come out ahead?
Of course, if you are a tool hoarder like me you won't ever get further than buy used, but I guess that would still be "less stuff" than buying new.
On a related note, my favorite business that does not exist would be a chain of second hand stores that deals in all that "beach vacation crap" (inflatable rubber things, objects to enjoy and/or deal with sand/wind/sun etc) that tends to get hauled home just to die silently in an attic. It would absolutely have to be a chain to make experience transferable between destinations.
All the extra tools, parts, and such that I have fit into two normal sized moving boxes, which can easily be stuffed under the bed or take up a shelf in a closet.
I have more of a problem with books than I do with tools and parts.