Quote:
why do we all have long hair?

Indeed, that probably isn't just some coincidence

According to memory, long hair (then) may be potentially 'low maintenance', and probably, from mostly a hair up-keep perspective (excluding serious washing), lower maintenance than just shaving it all off periodically (now).
However, it tends to get in the way, and can be grabbed (somewhat easily!?), if not bound up into a tail.