I try to answer your questions in short:
I started collecting 4 years ago with the Pro Kennex Ceramic Destiny. It was a good feeling to own one: this line was advertised massive in my childhood (in car magazins, tennis magazin) but I/we couldn't afford a graphite racket. After came the rare Dunlop Max 500i, Donnay Formula Pro..
I don't remember why I started collecting them, I just wanted to play tennis summer that year, and it was interesting to try out different rackets. At the time I didn't know about widebodys and racket stiffness etc.
Later I tried to make money from them: buying cheap, selling high, but I only sold a few, mostly to resellers: Cyan Vacuum Pro, New Pyramid Tour 630, Twin Tube Radical MidPlus, Pro Tour 630.
I played last time 3 years ago. In 2019 I tried to play, but was unlucky, as in this year.
I began the year with ~50 rackets, and I'm now at 60+. Just to much.. I wanted to try selling some of the rackets not pictured in this thread (exept the S. FP), but the Virus backed my plan.