The airlines redesigned first and business class to function better in the allotted space. Why not economy?
They have. But you and I have different opinions of what better means than an airline.
New airline seat designs squeeze in more passengers
http://www.foxnews.com/travel/2014/04/21/more-uncomfortable-airline-seats-squeezes-in-more-passengers/
Flew to Austrailia in ‘08 on an airline I can’t remember, but I remember the seats. I flew economy plus and I could spread my legs out completely beneath the seat in front of me. Same seats, just higher. What a concept.
Because then folks wouldn't pay extra for business or first.
I did ride on one domestic flight with shell slide forward seats. Seems like a really good idea.