I don't think HAIR (the original in 1967/6

inspired much of anything but it attracted an audience who saw their concerns being reflected on stage in a contemporary format. It did break some taboos as far as language/nudity and open displays of sexuality on stage.
RENT was Larson's attempt to meld traditional Broadway story-telling with an urban contemporary sound, but again aside from attracting a youthful audience to the theatre it did not cause any major social upheavals.
Rock music by its very nature is angry and aggressive. Sometimes it can be used to exhibit joy, but the range of emotions it can inspire is limited. Part of the problem is that very few rock musicians are trained in any other style of music, and they tend to think than an album of songs thematically linked will automatically transfer to the stage. These shows (AMERICAN IDIOT being the latest) are put on by people who do not understand or bother to learn about the musical theater's history. They don't know how to use music in a specific scene to heighten emotion. (They also seem to favour burying the vocals which runs counter to what good theatre is about: The text!)
I think it is wonderful that shows such as RENT, SPRING AWAKENING and NEXT TO NORMAL have attracted a new generation of theatre goers, a group that the industry had pretty much ignored from the late 1960s through the 90s. But it seems the only thing that they have been inspired to do is to go back and see the same shows over and over.
Cast albums are NOT "soundtracks."
Live theatre does not use a "soundtrack." If it did, it wouldn't be live theatre!
I host a weekly one-hour radio program featuring cast album selections as well as songs by cabaret, jazz and theatre artists. The program, FRONT ROW CENTRE is heard Sundays 9 to 10 am and also Saturdays from 8 to 9 am (eastern times) on www.proudfm.com