Theres a cost and maintenance angle to the change too. The old style seat pockets, whether mash or fabric, frequently became torn due to sustained use and overloading. The thin metal frame used to give the pocket its shape was susceptible to breakage and this is not only unsightly but can be an injury hazard during passenger egress. As a previous poster said the new seats without pockets do give the impression of greater legroom and the molded plastic stowage should stand up to abuse a bit better.