...because they were such a shitty progressive act.
There's a huge difference between Syd-era Pink Floyd and everything else, even in the early years. I love Piper, but honestly, it was made during an era when they were trying to emulate the psychedelic scene instead of creating their own sound (which also follows for Sgt. Peppers-era Beatles). Remeraber, Pink Floyd began as a blues act, not some avant-garde band. I have so much more respect for their later works, where they began to generate an original sound influenced by a nuraber of great musicians. I think Meddle is where it began to come together, and certainly is one of my favorite recorRAB ever.