On the hook
Mentorship works for two reasons. Certainly, the person being mentored gains from advice and counsel and even access to others via introductions, etc.
But mostly, it works because the person with a mentor has a responsibility to stand up and actually get moving. The only way to repay your mentor is by showing the guts it takes to grow and to matter.
Interesting to note, then, that the primary driver of mentor benefit has nothing to do with the mentor herself, nothing beyond the feeling of obligation the student feels to the teacher. Whether or not the mentor does anything, this obligation delivers benefits.
We can simulate this by living up to our heroes and those living by example, even if we never meet them, even if they've passed away, leaving us nothing but a legacy to honor and live up to.