As someone who has fought both with and against spears, I'll weigh in that using paired spears actually loses you a lot of the benefits of a spear used in one or two hands.
A spear designed to be used in two hands can be much longer than one used in a single hand, meaning greater range, and in the majority of fights range is life. The second hand also greatly improves the handling of the spear, allowing you to make deft motions with the point to change thrust alignment or draw out enemy defenses; many of the fights I've lost against spearfighters have been due to a feinted thrust using the upper-hand point control to strike me where I'm not defending. The haft of the two-handed spear is also usable in a fight, and is a surprisingly effective defense and alternate weapon.
A single-handed spear loses many of the benefits of the two-handed version. It's no longer nearly as deft or fast as the two-handed spear, and can't be as long. It's also much more difficult to use the haft, as you can't lever it forward or support it like you can with two hands. 358
Nevertheless, the single-handed spear has a niche role in conjunction with the shield, as shown by historical hoplites. The shield allows a fighter to nearly match the range and strength of the two-handed spear, as they can use their full body weight behind the spear and use the shield to cover the long recovery.
Trying to use a spear in either hand loses nearly any benefit. You can't feasibly devote your whole weight or reach to any strike as it both leaves you open while you recover, and means that your second attack will be very slow in coming. You can try to devote one hand to attack and one to defense (the most practical way of two-weapon fighting) but the weighting and construction of a spear doesn't lend itself to covering a line or to oppressing a weapon, so the defense aspect won't be very effective. Furthermore, on the offense, the one-handed spear isn't quick or versatile enough to take good advantage of the opportunities provided by its off-hand twin.
This isn't to say that twin spears is a style that's useless or impossible; it's simply overcomplicated compared to two-handed spear or spear and shield, and ineffective compared to equally complex styles such as paired swords, sword and cloak, sword and parrying dagger, and the like. 358