You've been unlucky, we get frequent power cuts here and never had any damage.
But one thing worth mentioning, we had one a few weeks ago, power was off for about two hours while engineers attended at the village substation, after which power was restored but my microwave failed to heat my lunch. I picked up on a few other symptoms, like a fluorescent light that was slow to come on, and checked the mains voltage... 180V, way below the minimum.
After I called the supplier and moaned about the low voltage they quite promptly returned to the village and waved their magic tools around once more, after which mains was 238V and microwave functioned perfectly.
Without sounding arrogant, I'll bet 9 out of 10 other people would simply have assumed the microwave was deceased, rather than checking supply voltage. The supplier would have noticed eventually of course, but that could be days later.
Excess mains voltage could equally be the problem, and maybe more likely to cause damage. Easiest way to check mains voltage is a plug in volt/watt/VA meter, circa £10-15 from Maplin or Amazon, iirc.