I think one reason some people find skill challenges "all grind" is frame of reference (or lack thereof).
I found my first few combat scenarios in 4E extremely bizarre. Nonetheless, the board game and the powers combine to create a conceptual space with a kind of Lewis Carrol logic one can manipulate. A well-designed scenario gives one plenty to manipulate, creating an engaging intellectual exercise. A poorly designed one degenerates into a dull dice-fest.
Now, I understand that some other players came to the game with a grounding in the "cheese" of certain video games that made some aspects familiar rather than befuddling and "cool" rather than dreary.
Whatever the equivalent formative influence would be for getting into skill challenges, my impression is that it's much less common. I certainly have not seen video gamers enthralled by watching virtual dice roll. They seem in general to be as much into exploring and manipulating their game environments as old-style D&Ders, to enjoy making real decisions and devising real strategies.
The combat game happens to involve a lot of dice-rolling, but beyond a point that's just a necessary evil. Stripped of the complications that make for interesting choices, it is in itself not all that much fun for many players. I wonder whether the designers overestimated the value of that game element, perhaps due to feedback from a play-test demographic?