If your favorite songs get obliterated by clapping and shrieking from some drunken idiot standing too close to the microphone, that's all part of the pain of securing a real-live performance in the raw, cutting out the record company and the retailing middlemen. What's more, a bootleg might catch moments of inspiration that would otherwise never have been heard, and never will again. It's like defining the news as something that somebody doesn't want published. Pearl Jam's gambit is typical of the control-freak tendencies of the modern music industry, where every last riff and drum sample is legally nailed down and audited. It's similar to the new gimmick of leaking snippets of new material onto the Internet, giving the impression that the audience is being offered something rare while actually being nothing more than a loss-leading device to boost conventional retail sales.
Record companies are monopolistic by nature and dislike competition of any kind.
As the music business has developed from the more idealistic years of the '60s and '70s into today's capitalistic monolith, attitudes to bootlegging have changed accordingly. While it's possible to find bootlegs of just about any act that ever walked the face of the planet, a body of key performers welcomed pirated material as tools to further their careers. The Grateful Dead disliked professional bootleggers but actively encouraged their audiences to tape their sprawling live shows. Consequently the band's career has been documented in frankly unnecessary detail. The case of Bruce Springsteen is particularly piquant.