Looking at the My Activity details is actually pretty creepy. Starting today working backwards, Google includes "Used Phone," "Used [my launcher]," "contacted [messaging site]," "Used [alarm clock app]," several overnight repeats of the messaging site when I received alerts, my Chrome-based website visits from yesterday, my foray into Android Settings yesterday, etc. It all serves to make me happy that I'm using Fire…
It's just that Google shows it to you, rather than not telling you anything.
Any sufficiently big Android/iOS app has the very same system in place so that they can see what people are doing with their app and anticipate interesting features, down to the location of your finger when you touched that button, the wifis you were seeing at the time, the battery level etc.
Admitedly though, Google has such a wide reach in all your day-to-day life that they gather an immense amount of data.
But don't be fooled, anyone else is also doing it. And they are far less open about it.