Watching TV and movies is actually an exercise in concentration. If you stop doing it and only use the internet, you find it becomes difficult to sit still for long enough to get back into them. A show or film feels way too passive and un-engaging by comparison. If you're on your computer or phone, you feel sort of plugged in. You're typing, you're switching sites or browser tabs, you're doomscrolling. Basically you're changing what you're exposed to in a quickfire sort of way. If you then try to go back to older forms of media, they can feel stagnant and hard to focus on. Your mind is guaranteed to wander. I've had the same thing happen.