Why Bother?

Why bother? Should I join the American Association of blah-dy-blah-blah of blahs? This is a question I asked myself while I was in graduate school, and it was the subject of a conversation I had with my other grad school friends.
I remember in particular a society that offered joint membership with another society. Purchasing joint membership in both societies was cheaper than purchasing individual memberships in both, but more expensive than purchasing a single membership in either. The conversation went like something like this: