Yes, it's because it keeps changing shape. Basically the skin stretched over your skull is always the same shape. But the skin stretched over your neck muscles is continually changing shape, often quite drastically. It gets all concertinaed up if you look upwards, and if you look down you are probably stretching it an inch or more longer. If you bend your head to one side, it is being stretched at one side and crumpled up at the other. All of that is bound to put a lot of stress on a piece of non-stretchy mesh.

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One other thought (perhaps a bit frivolous, but intended to be helpful): if you have a thick muscular neck, you can get away with a haircut which ends at the occipital ridge or just below, see for example the guy in the top photo on this page -

http://www.network54.com/Forum/241571/th...+you+tried+-

- whereas if you have a long thin neck, the neck hairline seems to have to come down lower. So one thing you could do would be to build up your neck muscles.