I don't know about you, but if i handed you a CD of music I created and said "spread the word and help me sell this." and you replied "Ok, I'll get 80%-90% of the profits" is that fair? That's exactly what majors do and on top of that they'll give you a "signing bonus" or "advance". "Okay if you hire me to push your music I'll give you $200,000 to put towards making the next album".
fine print in contract that you don't read: "but you owe me that $200,000 back later after selling the music"
so because I get $1 for every cd I sell and 10cent for every mp3, borrowing that $200,000 means I need to sell either 200,000 CDs or 2,000,000 MP3s before I actually get any money for myself, I'll sell 200,001 CDs and get $1 in profit.
Dave Matthews mentioned denying contracts with major labels that wanted to sign him. "Fine have the major take me out to dinner" he says "why would I sign with you? I'm already making money." That's because independents work directly with their PR, Manager, Sales, advertising, etc. and they give maybe 30% of their profit away to those entities and keep 70%.