Jefe Bergenstein
Legend
A character is more than a class. A character is also Ability Scores, and a Background, and a Race, (and Feats, if you are using those), and what-the-player-does-in-play.
Using all those tools it is possible to have a fighter PC who is perfectly able to participate in exploration and social aspects of the game. Why does it matter which particular aspects of the game mechanics you use to accomplish this? You should look at the character holistically, and worry less about the components.
And if you used those same tools on a class with other abilities baked into the chassis, they contribute more. The fighter really gives up too much for a non-existent advantage in combat. A paladin has those same non-class tools, spells, and gets to use his social stat to pump his party's defense. The champion in particular is just egregiously boring and not even particularly good as compensation. They could have at least let remarkable athlete stack with proficiency bonus, scaled second wind, tossed them an extra skill, etc.
I think Xeviat hit the nail on the head. It's for people who just don't care about mechanics or if other classes get more. And because so many just don't care, it will remain the "kid brother button masher" class. It's "mostly fine" and that's good enough for them, so they'll continue to shout down anyone else who dares ask for more. Hell, probably a good number are basically run on autopilot as a second PC to someone's caster. That's what we did in 1st/2nd edition. Fighters/thieves were henchmen, your "real" character was the mage. At least Ars Magica formalized it and gave everyone a magi and a bunch of grogs.