You could apply the same question to anything: should you learn Maya? Should you learn how to be a boom op? Should you learn how to break down scripts?
If it's relevant to you - go learn it. Don't learn something simply for the fact that 'it's cool' or 'everyone else is'. It seems to have no relevance to you, so why should you learn it? When/if you need it, you'll find someone who knows it a lot better than you could have. There are many who 'kinda' know a bit of After Effects, and very few of them are getting jobs for it - some of them might use the little they know in some of their films, but I guess you have to weigh up whether it's worth the time spent learning for what you'll actually end up using it for.
I learnt it, and took some AE classes in film school. It was cool, I guess, what you could do, but I haven't used it since.