1.  They fascinate me since I could think

2. the material is the most lasting for MTBs, leight weight as alloy &  titan and it is repairable

3. all details from welding artists make them simply beautiful, especially fillet brazed frames from Joe Breezer and tom Ritchey (but there are so many other nice out there, so I started collecting them)

4. this article hit me deep in my collectors heart when I build my Bontrager OR . Thanks Mountain Bike Action.