Wii Warm Up: Guitar Hero Redundant Edition

A (mostly) single-band Guitar Hero game focusing on Aerosmith came out this summer. It's being followed up with Guitar Hero: Metallica, which features Metallica and a bunch of other bands that Activision's marketing department thinks people who like Metallica also like.

Given the fairly customizable nature of music games, thanks to DLC (and, to a certain extent, Guitar Hero World Tour's music creation), is there any point to a single-band game like this? Is it in any way preferable to, say, making a bunch of Metallica songs available as Guitar Hero DLC? Harmonix's Beatles game seems to avoid this issue entirely, since the company is apparently making a different (not Rock Band) game around the Beatles' music.