There is a practical reason for directional markings, but it's nothing to do with the cable itself considered in isolation.
An analog audio signal has alternating polarity, so in regards to the behavior of the cable itself, directional signal markers printed on the cable jacket are meaningless. That is unless the cable was somehow designed to act as a rectifier, which is not what one would want nor how standard audio transmission operates.
However, in a completed cable assembly such directional markings on the cable jacket can be helpful in indicating the orientation of the terminations, and thus the correct orientation of the cable with regards to the two pieces iof equipment it is connecting. Consider a microphone cable. Because microphones generally feature a male XLR output connector while preamplifier/recorder inputs feature a mating female XLR input connection, the directional markings can indicate the practical "directionality" of the cable from microphone to input. This can be useful in setting things up under pressure. Such as reducing the likelihood of making a mistake when laying out a long cable run only to discover it when proceeding to hook things up.