I know a lot of us feel like we could quit on the team sometimes, but I think most know that they never actually could. Short of it being revealed that the Cubs were facilitating some kind of heinous human trafficking/exploitation operation or affiliating themselves with a hate group or some such thing, I don't see any way I could just stop being a Cubs fan. I wouldn't be so sure of that. People's life situations change all the time. And especially as people age they tend to care less about a pro sports team. On the whole you aren't going to see a mass exodus of fans. But I could easily see people just stop caring/paying attention. It happens every season on a smaller scale, why couldn't it happen over a longer term? And I wouldn't just assume somebody "wasn't much of a fan" if they ever did stop caring.