If you look at a gravel bike more like a "common sense road bike" instead of a watered down MTB, they make a lot of sense. You can ride in most surfaces, add accessories like racks and mudguards,...
My only issue is that they come with drop bars, which most people don't want/need, but buying a hybrid, which would be the same thing, is deeply uncool.
In Germany people call hybrids "trekking bikes", which sounds better, and come equipped with dynamo lights and most other required stuff. Good for 80% of users, the younger crowd goes for the gravel stuff though.
Unfortunately, some newer gravel bikes are losing the versatility that made them great, either going for much thicker tires (just buy a hardtail) or removing all eyelets for accessories (just get an all road racing bike)