Why it's so hard to put the phone down
Notifications, likes and infinite feeds work through intermittent rewards: you never know when something interesting will appear, which keeps you checking. Researchers use terms such as nomophobia (fear of being without your phone) and FOMO (fear of missing out) to describe related patterns.
Problematic use isn't measured only in hours, but in what it displaces: sleep, attention, conversations and the ability to tolerate boredom or uncomfortable emotions. Small changes, like notifications off and phones out of the bedroom, make a big difference.