I'm surprised many of these aren't obvious to you.

tab is 'active', the fuck?!?
A website serving a video will need to know if you're actually watching so it can stop playback or if background playback is desired, they know they can lower the quality of the video being delivered to save bandwidth.

Light/dark mode?
Sites are often designed to align with the light/dark theme set in the browser or OS.

battery status?
Less demanding objects are often delivered to visitors with low battery.

gpu
Some objects being delivered benefit from knowing which drivers/GPU they need to be compatible with.

etc. etc.

The creators of a browser doesn't benefit from providing this information. It's all stuff that can sometimes result in a better browsing experience and since the browser doesn't know which sites would, it provides the information for every page load in the handshake.

If you don't like it, use a privacy-focused browser or an extension to randomize the data.