People play on the same device when they hang out with friend in real life. People play on the internet when their friends are too far away to hang out in real life. Playing over LAN means playing with people in the same building but not meeting in person, which is a less likely situation.
I mean, it does happen. I have personally played LAN games with family members in different rooms in the same building. But it’s still a less common way of interacting. Most people prefer to meet interact face-to-face when the people they’re interacting with are nearby. Most people prefer to play networked games with people who aren’t nearby. Exceptions exist, of course.