Why should a dragon care if you are able to not pass out at what, to it, is room temperature? Look Mr. Dragon, I haven't passed out, aren't you impressed!
That depends on what you are defining as a "success"... In the context of this particular part of this particular skill challenge. Success equals the group NOT reinforcing the dragon's view of humanoids as slow, squishy, weak little bits of tasty snack food that make funny noises when you poke them too hard.
As a fictional trope, it's the "Heh! Not bad for a [insert demographic the antagonist looks down upon]!" moment. The dragon's not necessarily impressed, but he's just not displaying his usual dismissive disdain toward the percieved weaklings standing before him... which when dealing with a dragon would be considered a success from the party's point of view.
Whereas a failure might elicit a, "What's the matter? Too hot for you?" as the dragon mocks them and laughs at them.
And a neutral result would be ignored.
Forcing everyone to be involved in all skill challenges is bad. Just don't do it.
Why not? We force everyone to be involved in all combats.
What's wrong with looking for excuses to make non-combat encounters interesting and fun for everyone?
Have you tried pushing them on this? I needed to remind them that they could use other skills if they could rationalize it, and I ask them how their skills are helping them succeed.
Oh, absolutely... Just, some of my players grok the idea better than others. Recently, during a skill challenge to track a band of hobgoblin raiders to the ruins they were using as an encampment, the party wizard, who wasn't very good at the standard tracking and wilderness skills, suggested that he could use his History skill to tap knowledge about the ruins in the area and narrow down the possible destinations. It was a great idea. I let him use it, and gave him a "personal milestone" for it.
On the other hand, during another recent, very short, skill challenge to calm the fears of a rescued hostage and get some information about the enemy from her, it amounted to the cleric rolling Diplomacy four times in a row "I try to calm her down, and tell her she's safe" with everyone else aiding... Even with hints and suggestions for other possible skills they could be using. Blegh.
In other words... I know my players. While they do have their flashes of brilliance, often enough they need to be led by the nose.
Then I narrate it to make it even cooler.
Yup, yup...
Again, some of my players are better at doing this on their own than others (Once, when I encouraged a player to describe a particulatly spectacular critical hit, he said, "I hit him really hard with my sword."

You gotta love him.

), so I try to help out by setting an example and giving a little post-hoc description of what they did.
One important thing: never give a skill challenge that stops the adventure cold should it be lost.
Oh, absolutely.
For example, when the party ultimately failed the challenge to track the hobgoblins, it didn't result in them not finding the hobgoblin's lair. Instead, it meant that they trigger one or more random encounters, and were delayed by a day or two... Consuming valuable resources, and increasing the chances that one or more of the hobgoblins' hostages would die befome they could be rescued.
I always looked at skill challenges as either success == extra benefit, or failure == extra complication.