Time invested

The players are all 3rd year university engineering and a computer software guy? (computer science student, I believe?). All enjoy the game and prefer Pathfinder to 5e but they refuse to invest time into the game.
It always confused me as to why someone would enjoy something so much but yet not do the work associated with it. Lots of work, yes, but a small amount attached to your hobby perplexes me.

I get a difficult or confusing but say a easier game that you have played for months is hard to wrap me head around?