Bandcamp has been heavily used by many hardcore punk bands for a few years now. The ability to charge a reasonable price for high quality downloads or give them away for free and also sell physical media like records and tapes is a huge deal for lots of punks. There's been several ways of digital distribution of music before Bandcamp, but few of them offered an easy means of getting up and running and monetizing the music in multiple ways (if desired, that you don't have to at all is super important here). It's really the convergence of features rather than any one in particular.

I think for punk bands that might not even be on a label being able to get your music out there without a big upfront investment is more important than artists on larger labels because in that case distribution is usually at least partially handled. That's why the hardcore punk scene has been somewhat of an early adopter of Bandcamp when compared to more mainstream artists.

Also, the band the article mentions in the first paragraph, Mace, is totally worth a listen. Definitely one of my favorite bands coming out of the Midwest right now. If you can get your hands on volume 2 the "No Friends" zine it comes with a flexi that has them and some other great stuff on it.