Not all favors should be thanked. Favors you do need, you thank, you must be grateful. Favors you never need, you don't thank. In fact, you can take them, I see nothing wrong with that, make them useful to yourself and not be thankful. But thank God, always.
Of course, not being thankful does not mean not to say "Thank you", even though that can be a valid option. Saying "Thank you" can mean many things other than being thankful, such as "do not be discouraged by my ingratitude" or "if only that will shut you up", etc. It's the only good thing to say without discouraging the zeal of the favor providers, if there's a better response to use, I would use it, but I currently find none. The expressions of it will distinguish it all. Accepting such insistent but unwanted favor, is better than fighting it off, or than saying "No, thanks" in some cases.
For example, someone helped me in my court case, I am most grateful to them. On the other hand, someone helped my wife got a job where it was not asked of them, that I'm not thankful to them for, though we have double income because of it.
What then? Must favor be granted only when asked? No, not necessarily, wise judgment is required. This results in stronger relationship, understanding, fine tuned sensitivity, responsibility building and better ability to care.
But in all things, I give thanks to God my Lord.
Now, this principle of mine, will certainly drive many pastors who love to create unnecessary favors up the wall. But it is okay. They'll learn.