In a utopian world yes the fighters would always get the best deal for the fight. Unfortunately companies like Pride, UFC etc sign up fighters based on how much revenue they will bring to the promotion & fighters sign for the guarenteed salary.
Title belts don't always mean as much as a lot of people think. Frank Shamrock Vs Cesar Gracie & Royce Gracie Vs Matt Hughes sold the most seats in the US (so I believe), yet neither had a belt on the line.
The are some promotions that are more fighter friendly (WFA for eg) but I cant think there'll ever be a time when promoters stop signing fighters on long term contracts.