Originally Posted by
TimmyT
They are cool-lookin'
The original reason, apparently, was to create both strength and flex in the rear triangle; but, for the most part, the Colonel is correct.
A lot of English bikes wound up doing this. Notably, the Bates bikes had a bunch of curly stays and forks.
Bates' patented and easily recognizable Diadrant forks came along when they started building their Cantiflex frames which were stiffer than anything you could buy at the time and the fork was designed to better absorb shocks while actually being a little stiffer in corners than a conventional fork.
The Diadrant fork was also very recognizable in an age when a maker could not advertise their bicycle in sanctioned races just as Hetchins' rear stays are unique.