Obviously the sitter thinks there's a point in it. That's what counts, I think. As I see it, it's my job to read the cards, not to pass judgment on what questions my sitter asks or how often they've asked the same question or how many other readers they've asked that question. As AJ says, it's your prerogative to set limits on who you read for, how soon or often you'll read on a specific question from a certain sitter, though, so you do have that option.
Personally, I don't keep a running tally of what questions the sitter has asked other readers. That's none of my business and I have better things to do. There are cases where the sitter may just want a reading and not be able to think of anything but the same thing they've asked before. There are some cases where a person is lonely and just wants some reason for some human contact so they ask me for a reading. And there are cases where it's harder for the person to let go of the question.
I do get tired of hearing the same question from the same sitter over and over again sometimes, but usually the cards just say the same thing again in the next reading. It just depends on how many times they need to hear the message before they give up hope.
I don't keep track of what questions my sitter asks. Once a reading is done, it's usually just gone from my memory. I think it's supposed to work that way. If the same person comes to me with the same question for three years running (and it has happened to me) then I'm more inclined to remember them and their question, but I don't usually remember otherwise.
I'm not God so I can't say that any sitter is going to reader after reader and asking the same question is doing it with the hope they'll get the answer they want. I can't read minds, I just read the cards. Their reason is their own and none of my business. It may not always be that they're looking for one to give them the answer they want to hear. They may be doing it for some other reason I can't even guess at. Sometimes a sitter gets a positive answer and still asks the same question over again so it's not always that they're doing it to hear what they want to hear.
I think it comes down to the question "Why do I read?" Am I doing it for myself or am I doing it to offer a compassionate service to others? Do I have empathy for my fellow human beings or am I just sitting in judgment on people to feed my own ego? Those can be tough questions.