He reminds you (and everyone else) how relevant he is to your success.
I never miss an opportunity to thank that same high school friend from earlier for all of the late night rides to campus and flat tires he drove two hours to change when I finally got my own car. But if you have him tell it, he deserves credit for anything I ever achieve in my career although it’s been almost 5 years since I was an undergrad. Driving me to school doesn’t mean your name should be on my degree too because frankly, he wasn’t with me in the library typing up term papers. A resentful man will hold the smallest favors over your head forever.