One of the points of the Manifesto for Software Craftsmanship is about creating a community of professionals. Why is a community so important?
In my early career years, I didn't care too much about communities. Of course, Meetup wasn't very famous, and apart from Java User Groups and Linux Groups there weren't many opportunities for networking.
When doing our job, specially if employees of a company, we end up talking about problems we solve and technologies only with our colleagues. This gives us a slightly limited point of view, as it has always happened with every kind of society only with cultural exchange some progress happened. By finding and participating in a local community, you'll get to know people with different stories and different background - every single story shared will give you a grasp of a maybe totally different world, broadening your horizons and improving your cultural baggage. It's also a good opportunity for networking and - why not - get a better job!
I started attending the events organised by the London Software Craftsmanship Community, and I really can't recommend them more. I already met some very clever people (way better than me!) and every meetup it's a good opportunity to share knowledge and learn new things.