Spears were more of a thing in every ES game before Oblivion. In the first games, there was a combat system where you swiped the screen with your mouse to attack in a certain direction (mouse support was still a little novel in games). Weapons had a thrusting, lateral slashing, and overhand attack, and they would do different damage with each one- for example spears or foils would do the most damage thrusting, swords when slashing, and hammers/axes overhand. In Morrowind the attack you did was determined by the direction you were moving, but they must have thought it wasn't a very fun feature because there's a box you can tick in the options menu that just makes you use the weapon's most damaging attack no matter what direction you're moving in. In most Elder Scrolls games, Spears were underpowered and didn't get much love anyway, doubly so once their unique nature of doing lots of thrusting damage (in exchange for poor slashing) didn't really matter. Also, apparently nobody at Bethesda though spears made a cool weapon, so by Oblivion (which completely removed the whole weapon-attack-direction thing) they were cut.
Come Skyrim, where there's really only unique animations for one-handed, two-handed, and dual-wielding weapons, Spears didn't fit in at all. Besides, in all practicality, if spears had a realistic reach it would devolve into the player running backwards while stabbing anyway.
If you want a game that handles medieval weapons realistically (well, moreso than any other video game) I highly recommend playing Mount & Blade.