Well, not everybody thinks about worst case scenarios.
What it really gets to is that there really aren't very good/affordable resources for artists and venues to reach a large audience.
Hiring a local "designer" is often really expensive and you end up with a crappy website that is hard to maintain.
Even using something as "simple" as WordPress can be way too technical for a lot of people.
FB has the benefit of giving them a platform that enables them to quickly connect with their audience.
I see it as a failure of the rest of the internet ecosystem.