Yes, it's a general direction of technology to move to streaming and digital (much to my dismay, considering the subscription model is popular with companies and horrible for customers). Hardware is abolishing CD/DVD drives, software companies LOVE that because the subscription model gives them money and "graciously" allows customers use of the software. And no, it has nothing to do with what customers/players want.
People wanting or not wanting games on physical discs is a completely different conversation. For a multitude of games and software, physical copies no longer exist. You only get a code in a box if you buy it in a physical store (I think GTW was the only one that came with a CD aside from base game. Maybe GT too, I'm not sure.). Unlike TS3, with TS4 it's not a difference between a disc and a code, it's a difference between a code in an email or a code on a piece of paper. I would guess this is part of the reason why stores don't stock TS4 EPs anymore, since they're not really physical copies anyway.
As for TS3, I haven't seen a copy of it or any of the EPs in any of the local stores in a very long time (exception: used copies that you can't link to your Origin because the code's already been used). None of them have it available, not even in their online store database.