Because I cant stand under-engineered fastener type stuff that you cant even see i made one out of a couple if different diameter reinforced petrol line (long bit with a short bit over the end super glued on ) its obviously oil proof but the main point is that it wont perish in 5 months like the modern replacement rubber bits,

Also whist i had the tank out ( what a mission) i got a guy with a MIG welder to weld a couple of triangular cleats in the corners of the tank bracket as they are notorious for cracking there due to vibration.......I also made the bottom mounts by super gluing a large diameter piece of petrol hose ( like gas pump hose) onto a bolt with a panel washer fixed to the head .......now those little cups DO get oil on them and rot out , naturally IF you can get replacements of those they arnt made oil oil proof rubber .......the things we do