It's never as simple as a global switch for your typical game scenario, even disregarding textures you want to sample with point or bilinear filtering because of various valid reasons, there are cases where you want to disable it for performance.
I'll give an example that happened to me to illustrate: in our hair rendering pipeline on PS3, we had to render hair meshes several times for various passes. The problem with that kind of meshes is that they often have a ton of overdraw because of the number of layers. Tons of overdraw means a lot of texture samples. In this particular case, AF proved to be much too costly for the increase in quality (especially since most hair strands are usually close to parallel to the camera plane where AF isn't as needed) so once we agreed with the artists that the tradeoff was acceptable, we just disabled it explicitely for some of the hair passes and got a significant boost of performance.
What I'm trying to say (like several time already in this thread) is that apart from a mistake made by some artist, there can be instances where due to lacking time to optimize properly, cuts are made where it's the easiest. Now wether a dev should cut AF or another feature is always debatable and the final decision always lies with the dev.
AF can be costly, but these are all multiplatform games. If a dev develops a game like Stryder for all 5 platforms, get's to PS4 and notices that AF isn't working in their engine and removes it, that's a problem. But it's not. The GPU on the PS4 should be perfectly fine of utilising AF in a similar way. If not, and the PS4 needs a special method, then Sony should help devs with it.
Otherwise that means we will be seeing this a heck of a lot more. We know devs leave out things, but them routinely leaving out AF is a problem.
Unless what you are really trying to say is that AF is just so effortless on Xbone in comparison.