It's what ensures that not every character can can effortlessly pull off stunts like this:
https://www.youtube.com/watch?v=Z1nYEH6EDwM and this: https://www.youtube.com/watch?v=Cm91hh9SqXs
That's what skills & stats reflect.
In Fallout 2, the PC without sufficient insight, was incapable of selecting/and saving the best brain to use for the robot. It was because their skill was so high that they had that option. In Planescape there were many conversations where the replies depend directly upon the PC's skills and stats; because that's what defines the PC to the game engine. In Planescape, for instance, the PC could spot a pickpocket robbing him, and [only] with sufficient agility, could catch the thief in the act; the less agile PC would be unable to match the agile thief, and they would slip away from him. Alternatively, the PC could opt to allow the robbery, and even study the thief's technique... improving their own skill for the insight.
The player in an RPG has sway over what action the PC takes, but the PC's background dictates what the PC is competent in. The player usually has the choice to improve the PC's competency in certain skills over time; but this [rightly] comes at a cost... The cost of not improving other skills instead.
The problem with all of Bethesda's learn by doing titles, is that there is no time limit ~sadly. If there was a limit to how far the PC can progress, and that improving skills made them faster to improve ~~while not improving other skills made them slower to improve, then the system would be far more RPG-like, and a better game for it. the player would have to decide what their PC was going to be, and be held to it. It would result in PCs that had affinity and aptitude for their favored actions... It would shape the boundaries like all RPGs should have for their possible characters... But of course, it's a bit pointless if they don't account for and support the PC's skill proficiency, and other aptitudes. , but that's just being a bad/poor RPG.
Of course they were skills; they were even called skills in the UI. As for weapon proficiencies, those are skills (that's a synonym for skill). Character classes are the PC's education and aspiration. It's what they chose to be in life. Spell casters too... Spell casting is a skill [for non-innate casters]; the spells themselves are skills, and they have to be learned to use them.