Chaps were designed to keep long grass from hurting your legs when riding your horse across the tall grass lands. Nothing to do with falling off a horse, never mind falling off a motorcycle.
For those that like the look of them, go for it. I really can't see the practicality of them, though. Anything you can say they do, pants do better. Other than framing your junk for people to admire, I suppose.
Brilliant my favourite post of the day... priceless!