I have boxes of cables accumulated over decades. Every other brand of cable is basically in the same condition it was when it went into storage.
But Apple cables are fucking disgusting (there is simply no other way to say it). Why are they so sticky? Why are they so yellow? Every Apple cable seems to be affected--headphones, power supplies,and dongles.
My guess is it has something to do with the "soft" touch finish and the white coloring.
No idea about why some plastics get sticky, though. I'd imagine it's the plastic's polymer literally breaking down, but it might also be some additive "sweating" out. Maybe it's the very same fire-retardant chemical. (Old yellowing hard plastics don't get sticky, but they don't tend to have plasticizers in them, so they need far less flame-retardant.)
I don't know how much truth there is to this theory though. It doesn't seem to explain the poor strain relief.
"Removal of BFRs and PVC were challenging since alternatives were not readily available at the time. The largest obstacle was identifying a replacement to PVC in AC power cords, where strict safety standards favored PVC and created barriers to its elimination. Apple worked with multiple material suppliers and tested dozens of different formulations until the right combination of performance and safety were achieved with lower toxicological and ecological risk than PVC. Apple then had to persuade dozens of safety agencies around the world to allow it to certify the alternative materials. Millions of PVC-free power cords are in use today with Apple products."
https://www.apple.com/environment/pdf/Toxicology_in_Material...
Investigating magsafe cable durability in those countries might be a way to corroborate or refute the PVC theory, though I wouldn't know where to start.
I have never experienced anything like this with other brands nor with no-name brick chargers. Even Chinese knock-off replacement cables for Magsafe chargers didn't fail like that.