Some comments here mention media queries, those are folks who are with the times, and care enough about their design to target it for a specific class of devices.
A few years ago, one could be either a print designer or a web designer. Web designers have worked hard for standard design systems like CSS for a couple reasons; the first is that we all lived through IE and Microsoft in the late '90s, and it sucked; embrace and extend soaked millions of man-hours out of the economy, and designers are still pissed about it. The second is that it just made sense to use conventions when really all that varied about web use for the first 20 years was bit-depth and resolution.
I'm a little bit of an early adopter, but I don't think my web browsing yesterday was totally unusual: I used a 1280x800 laptop, a 1920x1080 monitor, an 800x480 touchscreen device in portrait and landscape, and a 320x480 touchscreen device.
Each of those requires its own design attention; a conscientious design would probably have separate design work for the laptop, the monitor, and the devices. An OCD designer could have more like five.
Standards can't legislate away usability, usage needs or user interest in a device's capabilities.
All that to say is that :hover works great for some design needs, and frankly, it would be cool to have it on a capacitive touchscreen, but we don't. Or at least, we don't right now; that doesn't minimize it's possible uses on other platforms.