I agree, but people are deliberately not using them at the expense of good usability because that's the trendy design.

Many people are using them, just more subtly than you might think. Projects like Google's material design may seem 'flat' to the lay person, but it's full of delicate transparencies, animations and shadows. It's leveraging the technology, but in a very understated way.

Examples here: https://www.google.com/design/spec/components/bottom-sheets....

yup that's a great example. It's definitely step it the right direction to neutralize some of the extreme flatness we've seen.