Ehm, well, even if the "real" lance never broke (which it, you know, did); if the lancer hit their target and actually pierced a human body... are you telling me that they magically yanked it out and retrieved it while moving lots of mphs on the horsie?
Physics sort of dictates that they had to let go of the lance unless they wanted to stop while the horse and saddle kept moving (with a lot of unpleasant consequences to follow).
To be honest, once you hit (code it to be lost after one-two kills or something) with a couched lance, it should be spent, period. If you stab with it, or a lighter lance/spear, it would obviously not break often or at all.