It's not a matter of budget in this case, it's a matter of memory. Animations take up space in the same manner that character models, textures, level designs, and weapon models due. If you throw in another set of weapon animations, then you'll likely have to limit something else to compensate. Adding in spears could mean less weapon models per weapon type (i.e. scimitar, broadsword, longsword). So would you rather have spears or more varied weapon appearances? It's hard to say, but it's a call that the developers make.
In a perfect world, there would be an animation for every type of weapon. After all, a sword parries, slashes, and stabs, but an axe cuts and a mace smashes. To put it simply, technology still has its limitations.
Mh, what of using melee-animations of staves, then, in case they receive those anyway? DA2 did have those, and those would be quite serviceable for basic attacks. Include some jab- and impale-animations for greatswords which can be used for spears, and off you go.
Valid point, at least for Unsullied. That still leaves Meera, though for ASOIAF.
And Aiel. One of the most powerful military forces ever to exist in fantasy, and spear is their favored weapon, with swords being complete taboo.
Nice to see those fellows brought up. Keep in mind, though, they are still using absurdly large daggers on the side, which are pointed out as being quasi short-swords in Book VII of TWoT if I recall correctly. Of course, do never tell the Aiel that. 
Personally, I have voiced that I am all in favour of spears and pole-arms making an appearance beyond codex-entries in the past, and I still am.