Ranked 5-man queue was removed because at the time, there were actually many organized "professional teams" that competed for spots at the world tournament.
People that weren't on those teams couldn't win, and therefore decided it wasn't worth playing ranked. In an effort to keep the e-sports dream alive, duoQ was introduced to give the non-pros hope and keep them queuing.
Forcing people back to (essentially) ranked 5q won't work, because it didn't work before and the community hasn't changed in the direction that would support such a decision.
Pips were a later decision to increase rewards for ranked queue to try to get people back into ranked once the population died even more. Moving that to unranked will give nobody a reason to go into ranked unless they want titles. That would bleed the last of the serious pvp community dry, and give anet even less of a reason to manage the spvp mode than they have now.
