Motivation to stay? How about saving the world from future threats?
We're supposed to be heroes, not goody goody two-shoes, but in the end, heroes.
If you play a chaotic neutral or an evil character and think there's no reason for the character to stay, that's your own goddamned fault.
There's a reason heroes tend to be good, seriously, it's pretty simple.
Though a plot would be good eventually.
Most of these people tend to be heroes who have lives outside heroing. And have their own homes. Which they were kidnapped from.
Yes, I think wanting to at least see your parents or loved ones in person before you go to war, what with the last they saw of you being you getting kidnapped is a fair enough reason to go home.