There may be some places where trucks have a lower speed limit than cars, but there is nowhere that allows motorcycles to legally exceed the posted speed limit. No kidding.
2. Light weight means better acceleration.
The smallest, lightest motorcycle has the potential to beat the most exotic of sports cars from a dead stop. In the late 80's, a manufacturer once promoted a tiny little 454 cc (that's pretty small) motorcycle as able to beat a Corvette from 0 to 60 mph. Of course, nearly every street legal motorcycle can do the same thing, but it was tongue in cheek, and fairly amusing. There are times that you may get passed when you have stopped at a light or when a speed limit changes merely because that Rider and motorcycle weigh one sixteenth of your car or less. That Rider is capable of being at the speed limit long before your car or SUV, so you might get passed without anyone ever breaking the speed limit.
3. Top-speed wise, most cars are still faster.
Motorcycle engines just can't develop as much horsepower as cars and SUVs. This is not a rule, however. Some very small cars these days actually have motorcycle-sized engines in them and develop about the same horsepower, but a four or six cylinder engine car will catch and pass a motorcycle eventually. That's just the way it is.
In other words, that guy blasting past you doesn't have something faster, he is just being more stupid.