> Isn't any delay measured and accounted for in syncing playback of videos?

It can be, but your operating system needs to support it.

Support for audio delay compensation is pretty good on macOS. No idea about other OSes, though.

It works everywhere. There is not much to do with delay on interactive content though.

People use headphones for phone calls not just videos. The delay is annoying. Mobile phones already have lag compared to land phones and BT makes it worse.

Ever played games with bluetooth headphones? Anyway, who wants radiation directly aimed into their brains.