I think a "favor" is a one-time thing and like a gift. The definition says, "an act of kindness beyond what is due or usual." So, if one keeps asking for the same favor from the same person, it is like using the person and offering to pay is like the person is for hire? But the person didn't sign up for that originally, just the one-time extra as a "favor" because they like you or are just a "nice" person?

If you need something repeatedly, like a ride somewhere, I would hire someone or ask upfront, first time if you can pay someone to take you "every Tuesday at 4:00"; lay out that it is not just a one-time thing so they can decide if they want to take it on. What the favor is, too, can make a difference. If it's not something the person is interested in (I have a man who always wants rides to the liquor store to get his lottery ticket and I don't go to that liquor store (he has a specific one, has an unusual brand of drink he likes) or buy lottery tickets, think they are a waste of money) or out of their way (either literally or not where/when they usually go) then I would try to find some other way to get what you want if the person isn't interested.

A lot of people aren't motivated by money, especially the little bit one might get doing a chore for another, driving them somewhere or dropping off/picking something up for them occasionally, they'd rather have their time to themselves to direct instead of feeling tethered to what someone else wants/needs. But a thought there might be; do you have a solid relationship with the person other than asking for favors? If that is the only shared thing, that would make a difference too, I'd think. If you an find someone who you enjoy being with and who enjoys being with you, where there's a real friendship, I think there will be less resentment in helping you.