Too Much To Expect

Imagine that a certain professor is involved in two particular "service" activities that are rather time-consuming. We will call them Activity 1 (A1) and Activity 2 (A2). It doesn't matter what they are or whether they involve institutional service (to the department, college, university etc.) or professional service (to the wider community of people involved in a discipline). And let's ignore for now the fact that many of us are involved in more than 2 "service" activities in any given year.

As happens from time to time, people on committees or boards or other service groupings need to find other people to join them in these activities. Maybe someone left, maybe there is a regular cycling of people through these service organizations or units, maybe it's just time to invite someone new. So the people currently involved in this service activity (in this case, A1) come up with a list of names of others to approach about joining them, offering a wonderful new opportunity to do even more service and spend all that excess leisure time.

Now there is a list of names that needs discussing: who would be good to work with, etc.? It emerges that one criterion for eliminating people from consideration is the fact that some are also committed to spending time on A2, so it is unlikely that they can be involved in A1 and A2.

But.. wait a minute.. you are involved in A1 and A2! Why was this not an issue when you were invited to be involved in A1?

You have a hypothesis.

Does anyone want to guess what this is, or at least propose their own?