In European martial arts, quarterstaff techniques are usable with the longer spears. In fact there is a lot of crossover between the various polearm techniques. I think the difference is whether you're using the spear one-handed (alongside a shield presumably) or in two hands, and whether you're fighting as a group or individually. If you're using it one-handed or if fighting in a group, trying to swing the weapon around to hit with the back end is obviously a bad idea.
In a one-on-one situation where you're using both hands on the spear, there is the option of using the butt. Its obviously less effective than the business end, but if your opponent can close with you, it may be necessary to use the halfstaff grip rather than just choking up on the haft. Or course at that point, since your opponent presumably has a shield, you're generally better dropping the spear and pulling your dagger.
That said, a lot of martial arts display techniques involve spinning the polearm around in flourishes. That sort of thing gets picked up by the media and so a lot of character concepts based upon media tropes are going to fit the idea of spear spinning. The dividing line between the 5e D&D "Spear" and "Pike" is also rather fuzzy, but in general the principle stands for both.
