It's best when laws say how we must act rather than what we must have. I used to rollerblade for miles on roads -- they are a perfectly fast and reasonable form of transportation for anything up to a few miles.

Having said that, I could never go as fast on rollerblades as I can on a bike (except when skitching -- an insanely dangerous/stupid practice which I used to do on rollerblades to cover long distances really fast).