Just as a reminder, finesse allows you to use dexterity instead of strength for damage on weapons which are very light. Go find a two handed weapon as light as a dagger or a rapier. Good luck with that.
Even according to D&D rules, spears (3lb) have exactly the same weight as a Scimitar (a finesse weapon) and are only one lb heavier than a rapier, and you have to keep in mind the last two are wielded with only one hand, meaning that a spear wielded with two hands would feel even faster and lighter overall. If we are arguing from a point of accuracy then it is obvious that the spear should be a finesse weapon. Of course you need strength to be effective with a spear, just as you need strength to be effective with a proper rapier or a scimitar in real life, and going back to the one handed versus two handed argument you can argue that it would need more strength to effectively wield a scimitar/rapier than a spear. What finesse represents in my view is whether a weapon is fast enough, that with enough skill, reflexes and agility you can more effectively use enemy weak points, thus making it more important than raw strength alone and spears definitely fit that bill.