Why do road bikes have clip ons?

[limax2]

Clip-ons were first used on race bikes in the early 50's when telescopic forks became the thing to have. Naturally they soon became fashionable with the cafe racer set. I fitted some to my 650c.c.  B.S.A. Gold Flash in the early 60's before I progressed to a 500c.c. Gold Star which came with them as a standard option and was sold as a clubman racer. Both great bikes at the time. 
History lesson over.