It's not just the lack of strain relief. As 'paranoidroibot noted in a sibling comment, the magsafe2 cables have more of it, but there seems to be some sort of

It's not just the lack of strain relief. As 'paranoidroibot noted in a sibling comment, the magsafe2 cables have more of it, but there seems to be some sort of degradation in whatever they're using as insulation -- the magsafe end of my cable is noticeably yellow and stiff compared to the rest of the cable. In fact this is my second cable, the first one having failed due to the insulation splitting after showing the same symptoms. This is in contrast to my earphone cables that have thinner insulation and more wind/unwind cycles yet are still going strong.