Many years ago - shortly after September 11, I think - I had a conversation with my dad that had something to do with politics and world affairs (super specific, I know). He was lamenting how my generation wasn't politically active; how we "didn't care" like his generation did.
I don't know about you, but here's what's always happened to me when someone starts talking like this: I feel like I'm being lectured and like any contributions I might make to the conversation will fall on deaf ears, and so I stop listening. What my father was saying felt like judgment; like a statement of superiority ("our generation cared...yours, not so much"). And while I don't think what he was saying was unfounded or even necessarily wrong - people who are now in their thirties largely went through their formative years during a time of (relative) prosperity and political calm, which is not the kind of environment that typically breeds vast numbers of revolutionaries - it certainly didn't make me go, "Wait! You're right! SIGN ME UP!"
The conversation made feel guilty, and judged, and irritated. And a person who feels guilty and judged and irritated tends not to be especially inspired to join the community that's making them feel this way.