I agree with Sheldon that all cables should have in-line adjusters but for brakes I personally don't use them. For one, I am not all that particular on the exact brake lever throw. Secondly, it takes so little time to adjust at the caliper that even if I did need to adjust it, it is a 10 second job. In general, if an adjustment is needed, it is to tighten it so the previously clamped piece of the cable does not come into play.
I think it is more of a sign of the quality of a bike shop than an actual necessity.
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