It's marketing and progress. Sony produce a range of TVs that have different features, at different prices for different buyers. If they put all the hardware and features that are in the EX models into the CX models then Sony would only have a couple of TV models and they would go bust. Every year technology improvements mean that they can put new hardware and features into TVs for the same price as the TV models from last year.
I also have the CX523 and I chose it because it had the features I wanted at a good price. If they chucked in the Wifi hardware etc, I wouldn't have been able to afford it and Sony would have lost a customer.
Smart TVs are devloping at an incredible rate. The things that they can do this year just are not neccessarily possible on TVs from last year....technology moves on.