If Jeph wrote a plot where something happened at a show, it seems like it is a lot easier to move things along by having the characters just talk about it afterwards, the way Natasha did when her conversation with Amir just rehashed what happened at a concert instead of us getting a random one-off where we saw Natasha kick some dude in the face and then have it referenced later. If Jeph at some point wants to write a show plot and thought it would be fun to draw I'm sure he would do it, but since he seems a lot more interested in the interpersonal side of things now there's not a whole lot of reason to make it A Big Thing.
Also the whole timing/date issue, since time in the comic doesn't move at real time, as has already been noted, which probably explains why we don't hear them make as many Hipster Music Jokes as they used to.
Also, Marten stopped writing his blog because.... Pintsize started refusing to do transcription in anything but a militant German accent, and it made Marten feel like a music Nazi, which made him think his talents could surely be put to better use, causing him to start secretly looking for a new job at Pitchfork.
(Obviously)