A road bike tire is inflated to 80-120psi which give an aquaplaning speed of about 92mph.
A hybrid tire is inflated to 40-70psi, which gives an aquaplaning speed of about 65mph.
Bikes aren't know for traveling above 60mph, so wet roads don't pose much of a problem for bikes. Their tire pressure is so high compared to their normal speeds, that an unassisted human would really struggle to make a bike aquaplane. Additionally bikes can easily be ridden stably at walking speed. Unless you're riding on ice, going slower simply doesn't pose a problem.
As a result slipping on bike, because you can't cycle slow enough, just isn't a concern. In the only situations where it might be a problem, simply walking would be challenging, and driving would be idiotic.
