I know that I, personally, have had times on my road bike where I would sorta get into that zone, hypnotized. I would be focused somewhere else, barreling down the side of the road on training miles and notice (with a good tailwind) that I was easily keeping over 22 MPH or so according to my bike computer. I can only assume that if I was in a hurry, in an urban area where there was lots of foot traffic, that at those places where we must intersect, I might get pissy at having to "slow down" for someone not watching where they are going.
I'm not below the average standard of rider - and so - it doesn't seem to illogical for a law to be put in place that, although hard to enforce, could be used to regulate a cyclist if they decided to buzzbomb a crosswalk because they were off in lala land.