Combat is generally an RPG’s most highly emergent system. Combat is built upon a number of actors operating according to simple rules, which then produces unexpected and complex situations. There are dozens of different factors in play at any given time in battle: a single scenario involves dozens of player decisions, and is unlikely to play out exactly the same way twice. This emergent quality makes combat a tempting choice to form the backbone of a cRPG, since it offers a much higher ratio of entertaining possibilities relative to development time spent than a more static system (such as, say, dialog trees) would. Thus, combat ends up accounting for a huge chunk of playtime, which in turn makes combat-related skills the most consistently valuable skills in the game.
Further, because combat skills impact an emergent system, their use offers a wide variety of possible effects. Gunplay, for instance, can deal direct damage; it can injure particular parts of an opponent’s (or player character’s) body; it can detonate explosives; it can break parts of the scenery; and so on. It offers variety and flexibility because the system it impacts responds organically to its use. This, in turn, makes these skills carry more water in terms of offering satisfying, unpredictable results across multiple playthroughs.
By contrast, skills that are useful only in scripted systems do not possess these benefits. A skill check or variable check in a scripted event will always produce one of two (or, in a best-case scenario, one of a few) pre-generated results. Because each result has to be hand-crafted rather than arising emergently, such skills are much less efficient at generating interesting variations throughout the game, and tend to feature less heavily in wRPGs than those skills which directly impact the game’s emergent systems.