On the show, it wasn't
just because "it was a narrative"; Clark generally had good reasons
not to go barging around and powering his way through all of the challenges: often, the main challenges took the form of figuring out who he should go after in the first place (the "investigative reporters" part strongly implied puzzle solving; and while Clark's super-senses occasionally came in handy there in terms of finding clues, they didn't help him
at all in terms of figuring out what those clues
meant); and even when they didn't, Clark had character motivation reasons to restrain himself: he could have won Lois' adoration in episode 1 by taking off the glasses, but that would have completely defeated the
point of trying to get Lois to fall for
Clark, not
Superman.
And on the wider stage, Superman was hampered in his efforts to stop Luthor by a desire to bring him to justice through the courts: he could have ended Luthor's threat at any time by busting into his tower and tossing him out the window; but that would have gone against everything he believed in.
In short, it wasn't just writer fiat that allowed Lois to have such a prominent role on the show: there was also the nature of the challenges and the personalities involved — which, if
roleplayed*, could lead to similar results in an RPG.
Granted, this approach wouldn't work with the stereotypical group of "dungeon crawler"-mentality PCs. But then, that's where the aforementioned social contract comes in: if your players are dead set on solving all problems by brute force and aren't interested in restraining their characters for reasons of the characters' values, then obviously something like Lois & Clark or Smallville isn't going to work. OTOH, if the players are on board with the notion that violence isn't always the best answer (even if it seems so in the short term), then something along the lines of one of these shows is
totally doable.
And frankly, designing RPGs with dungeon-crawler mentalities in mind is a losing proposition. Certainly, there's a place for such a thing; otherwise, the Dungeon Fantasy series wouldn't be the success that it is. But it's not something I recommend baking in to the core assumptions of the game; especially when the game is supposed to be Universal. You need more emphasis on encouraging other styles of play. In GURPS,
Impulse Buys and
You Might Have a Point There provide a good start for this sort of thing.
This, rather than character creation and advancement, is what I use points for in my games.
* By "roleplay", I mean making decisions for your character based on what he values and how he thinks, not just what he can do.