I agree, I don't sense any "rivalry" between Chicago and Detroit. From what I gather, we have a pretty neighborly attitude to Chicago over here. I mean, it is the coolest big city close by; not that Detroit isn't cool, but in all reality you don't hear about people from Chicago longing for a road trip getaway to Detroit so much as it is vice versa. To us, getting a gig or seeing a show in Chicago is a fun treat. I know of many Michigan bands that start to "expand" and either move to Chicago or simply play shows there regularly.
Right now, The Metrotimes Blowout is going on, which is a pretty big deal (one of the biggest local music festivals in the country) and I know some Chicago bands manage to get a gig playing it (even though the point is that it is 98% metro-Detroit area bands).
http://www.mtblowout.com/
Like John said, the increasingly higher overhead for touring really weeds out a lot of the "wimps", sadly. Plus, I simply think that live music doesn't have the appeal/draw it once had several years back (as indicated by the shrinking numbers of live music venues).
On a side note, the Hentchmen still play out here and there, and they happen to be playing a small/intimate $5 gig in Ann Arbor next weekend (see this link: https://www.facebook.com/events/1473225816227529/) as well as the Blowout.
So, despite the "chance" they had a few years back, they are still rocking the garage, in the literal sense of the word... I, personally, love the band (one of my favs that came out of the Detroit "garage revival" of the early 00's).
