I'm in the latter category, but I don't fault anyone for being in the former. I sort of just assume passion/interest is normally distributed and the ones you see actively doing lots are the tail ends of the distribution.

I find the passionate ones tend to progress in their careers and thrive on that sense of achievement and the punch-in/punch-out types are happy just to hum along, take work and do it.

I think it's necessary for balance.