JAR and FAR regulations require the manufacturer of an airliner to demonstrate TO and Landing with a crosswind component of 0.2x Vstall, except that he must demonstrate 20 knots however low his stall speed is but doesn't have to demonstrate more than 25 knots however high it is. They usually try to demonstrate as much as they can find, but run out of time while trying to get the a/c certificated.
Good points. For non-transport aircraft (I forget the FAR part numbers) the 20 knot minimum does not apply. And for some reason, presumably legal, manufacturers prefer to demonstrate the bare minimum. Hence I fly a light aircraft with a 55 KIAS stall and an 11 knot max dem xwind component. It's certainly not limiting.