A group should not confuse willingness with unlimited availability.

The person who says yes readily becomes the easiest place to put the next thing, and each individual request is small enough to seem harmless. What accumulates is invisible to everyone except them, because nobody is looking at the total. Willingness is a disposition, not a capacity, and treating it as capacity is how good people get used up.

If you organize anything, look at the distribution rather than each separate ask. Count who has been given how much this season, and take something off the person who never refuses before they have to say so.