Microwave is going to be just as fast for quickly heating up a small amount of water, stove is plenty quick for larger amounts but I have an induction stove so it's extremely quick. If you look away, it WILL boil over. I don't see how a kettle could be quicker than my stove for the same quantity even if I had a 240v kettle, the stove is 240v but has a 50 Amp connection, compared to the 15 or 20 that a kettle would get.
Having a kettle would be one more item to clean, store and have counterspace for.
Also if someone really wanted (and it made much of a difference) you can get 240v outlets put in here. Like I said, the stove has 240v so you could probably tap into that circuit to retro-fit. But I'm not convinced it's any quicker, or easier than just microwaving it or using the stove, so nobody puts those in.
Also, like the other person I've never had a pyrex handle heat up, and even with regular mugs put in there it only heats up from the food being in it, not being heated my the microwave.