Because the overall gameplay balance and deph perfected in we9le/pes6 outweights the benefits of manual controls/360 dribbling in pes 2013 for many people still.
In fact ps2 gen games also have got manual pass which very underrated by most players, bloody hard to master it tho as controls not very convenient
theres more than just 360 dribbling thats updated in next gen. there are many aspects that make playing older ps2 pes games seem obselete in many ways.
But once u get into the game and lose your mind eg...a close game looking for a goal and u forget all graphical and technical issued a game like pes5 can be gripping.
I think thats why it can still be a great game. It can be tense and emotional lol.
But to pick up n play these days its obsolete.
Though IMO fifa 13/pes 2013 can also be intense human vs human so why go back?