Since Detroit is so cheap and has such a rich history, there's a ton of room for people to create cool little niche businesses that connect with the city's past. There are distilleries in 1930s-era factories and pop-up restaurants started by Michelin-star chefs tucked in little corners. There's a much different atmosphere when you're at a gin bar in an old neighborhood to a nightclub in the suburbs somewhere. And if you like the more traditional bar scene, all four major sports teams will be downtown next year, with a huge new entertainment district coming to the Red Wings / Pistons' new arena.
Beyond that, people like to be the underdog. Detroit went through worse than almost any other American city in history and is starting to come out the other side now. Many of the people moving (or partying) downtown are from the suburbs or the surrounding area and take it personally that it's still regularly trash-talked nationwide. There's a very positive "us-against-the-world" energy to the city and I think a lot of people feel a responsibility to encourage the "comeback" by supporting the businesses that are helping the area.
Edit: Sorry that feels very google it for yourself. I don't mean it that way. That's a good starting topic to find the other crazy things that happen here. The Dirty Show is another one.