People who join "slow" servers and then no-life the game and play 1 or 2 biomes ahead of everyone else -- why?

It seems like every group has at least one of these guys and I'm just curious what the mentality is.

Our server is specifically targeted at players who are busy adults, only able to play for a few hours a day at most, and willing to progress slowly. For the most part everyone seems to be keeping to that, and yet I have one player who essentially lives on the server and insists on pushing the pace 1 or 2 biomes ahead of the group. They have respected the rule that we don't kill bosses until everyone is ready, but everything else you can do "ahead of schedule" they are doing.

Personally I don't really care how much someone wants to play, as long as they stick to activities that don't hurt other player's experiences. I can spend a lot of hours in the game just building, fishing, exploring, etc. But I think it cuts directly against the intended group dynamics of playing on a server when someone else is doing content faster than everyone else. I don't know why people who enjoy this style of play even sign up for multiplayer, since they spend almost none of their time actually playing with others.

Sorry for the rant, and would appreciate if anyone has any tips on how to avoid people like this in the future. If I try to host another game I am thinking about trying to limit the server's uptime to a specific window so at least people can't be on grinding 12+ hours a day.