Units seldom used.

[Arryn]

Jotuns are expensive, both in gold/resources, and in supply. You get by far more bang for the buck with spearmen (or spear-armed huskarls if you're tight on resources) than hurlers. You can only afford to have so many Jotuns so you need to make each one count as much as possible. Hurlers behind the front lines aren't nearly as effective as spearmen *on* the line. Hurlers cost the same amount of gold as spearmen (while only half the resources) but their 10 protection (vs. 18 for the spearmen) and pathetic 5 defense means that you'll waste all that gold very quickly if the hurlers ever get in melee. They are simply a bad investment.