I travel quite a bit and I've never encountered one. Never even seen one at all. I've heard of Chromecast because I go on tech sites, but they're suspiciously absent in my bubble of reality. I'm an Android and Linux user too.
I ask because when I have travelled for work, it's the corporate hotels that have often baked a Chromecast into their TV experience, even to the point of sorting out their wifi network so you're only able to cast to the screen in your room. Their splash screen offers "live TV" or the option to "stream from your phone".
They often don't shout about the fact that it's a chromecast doing the work, but the telltale standby screen that shows up when you're not casting something normally confirms it.
What's frustrating in this thread is how many people are conflating the weird dongle product with the extremely successful streaming control protocol. Only the weird thing is being cancelled!
Chromecast first gen was in 2013.
Apple actually beat Google on this one in terms of time.
Come on man
Practically, this means that you can take phone calls, hibernate your computer, kill a source app on your phone, leave the house entirely etc. with Chromecast without interrupting whatever's playing on a TV or stereo, while with Airplay, playback usually stops in these scenarios. Airplay is also a bigger battery drain as a result, in my experience.
They both support AirPlay these days, I've never been able to use Google Cast natively with a TV here, which is a shame for my use cases (Netflix doesn't support it, and I generally don't like to have my phone connected to the TV via Wi-Fi for the entire duration of a movie).
Edit: Turns out LG is currently in the process of adding it, and Samsung seems to have support in some models as well, but it's definitely not ubiquitous.