I've seen that from some models made in ~'08-'09, the cables do not fray.

I have 2013 rmbp 13" I have handled my charger with great care avoiding as much twisting ant touching as possible, and after around 20 months, cable isolation just tore up by touching it.. It seems that cable isolation is made of such plastic, that it completely degrades after some time..

Haven't had the issue with computer cables, but had the exact issue with iphone cables. The plastic apple uses for their cables is just weird, with friction or stress (just the stress of looping it around) it seems to gain a slightly rubberised texture, bulk up and ultimately come apart over time. I do have hints on that on a magsafe cable-end, close to the magsafe where the little plastic clip usually sits there's a lot of friction and the cable has gone dark-gray, whereas on the rest of the cable the clip can just slide along.

+1 they are weird compared to other cables..

Compared to any other cable in the market Apple's cables feel, look and handle way different. When charger cable is new it feels rather hard and inflexible. But later especially in areas where you touch cable the most, it starts changing colour and starts feeling like old rubber eraser and after some more time cable starts falling apart, just like old dry rubber eraser would do..

Apple want's matt white cables, when usually they are glossy black. I have some super sturdy audio cables (very flexible, resistant to twisting, friction and sharp angles, etc.) which are matt black, wonder how hard it is to make such cable white?