It would be helpful. Some cables' measurements fall outside the normal parameters, and can cause oscillation with some equipment. That could be avoided, for starters.
I presume because they don't want to start some specmanship war, or to avoid people buying according to what they think are the optimal measurements for the big three (capacitance, resistance, inductance).
Probably because some very costly cables are very poorly engineered.
Probably because some cables measure very strangely, and the companies don't want/know how to explain why they perform well.
Etc., etc.