I must part of the minority. I don't give a second thought to selling tools when I upgrade them. I have several sets of tools (home garage, work van, and travel boxes) but don't feel it necessary to have more than a few extras of anything.
My first set of tools as a teenager was stolen, part of the replacement set was later stolen. My dad for the most part had junk tools and the few good pieces were carted off by family. The end result is no emotional attachment.
I started flipping tools a few years ago as a hobby, so I generally view most tool purchases now as temporary with an eye to making a few bucks. I do have a few favorites like my Rockwell 100 router and 126 door planer kit. I bought and sold three or four of those kits to get to the one I might keep a while.
I gave a few tools away but the young guy treated them as disposable for the most , he has probably lost most of them by now.
Hey buddy wanna buy some tools?