The original idea was to prevent the extra heat generated by Xenon headlights creating an issue with filthy lenses (for legislated reasons, not the earlier version just for cleaning), hence the squirt to try to keep them clean. Over the years there have been many attempts to get the headlights clean with a few different ideas, but most have just disappeared over time.
Saying that, you are correct that they aren't all that affective, even more so if you increase the time level between affective squirts of the washers. As for "all over the front of the car", you are right as mine goes everywhere, but that is mainly because of the pressure involved (a lot more than the windscreen ones).
At the end of the day we are all different and we do what is important to ourselves