I don't think it's an age thing, we serve coffee where I work and we get asked for it extra hot, by all sorts of people. When we first got the machine and training we were taught that it's brewed between 90 and 96 and served at around 60 when the milk is added, depending on the milk you need for the type of coffee.
If you're wanting it extra hot though, then it's going to affect the quality of the milk if you're having cappuccino or latte for example, the different textures of the milk happen at different temperatures and milk that's been steamed to just under boiling point will not be as good a texture as at 60 or even 70 for a cappuccino.
When I'm asked for that I make it clear that it's fine, I have no issue with doing it, but that the request will affect the texture of the milk to some degree and there's not a lot I can do about that.
The ones that send the perfect milk back to be hotter, and then send the hotter one back because the milk texture is wrong are the ones who make it hard, because no matter how hard a customer complains, I can't change the laws of physics.
Extra hot isn't an issue but it comes with downsides that aren't within my control.
Extra hot americano is a bit of a mind bender, because it's coffee brewed at 96 and topped with boiling water, it physically can't get much hotter, a degree or two at the most, If someone asks for it then I'll make sure it's in a warm cup (should be anyway, but I'll choose the cup in the bottom corner of the machine that's the hottest) and I'll get it straight off the machine and to the customer, but unless you want to inhale it as a vapour, I cannot physically get it any hotter than boiling point.