Some apps will misbehave if sensor permission was denied by default (e.g. video players that are expected to switch to landscape when rotating the phone). I think that's why it's enabled by default, to not cause confusion among beginners.
Also it's a permission only accessible for the user of GOS and not AOSP and most AOSP based systems (just like the network permission). Therefore apps are expected to have it by default.
Now regarding disabling them: I do set the default to disabled right after installing GOS and only give it to the apps that truly need it. The neat thing is that you'll see a notification whenever an app tries to access sensors and then you can decide whether it makes sense. I don't give it to apps I intend to use in portrait mode exclusively (e.g. AirBnB), but it's nice to be reminded when it might be needed. Don't change these settings for the pre-installed system apps, because sensors mean many things beyond compass and accelerometer and you'll probably break some functionalities down the line. Only user installed apps should be denied this in my opinion.
I'm not speaking for the project, just from experience.