But lots of times, skills are about individual success (do I jump the canyon). You are building a straw man. Most skills tests are not just about one member of the party getting the whole party through.
I'll have to say we have very different experiences on this. It's possibly because of the players I play with. If there is a check to be made, it only gets made by the highest modifier. When an NPC asks them a question, they immediately ask out of character "Who has the best Diplomacy again? Right, you should answer him. The rest of us, shut up, if we say anything, the DM might make us make a roll. That means you, Half-Orc Barbarian!"
Rule number one in every party I've been in has been "Don't split up!" So, the highest modifier is ALWAYS around to roll. There are exceptions, of course, but they are rare.
Or where the rogue with the +14 succeeding, didn't get the whole party through, because everyone had to make their own check and be judged indivudally by an NPC.
The thing about individual checks is that they often end up in a situation that makes an adventure unworkable. If everyone needs to make a jump check to get over a pit, then either the DC is easy enough for even the lowest skill or one person doesn't get across the pit.
Either the group continues without the one person who couldn't make the jump check and you make the player bored as he has to sit their and watch for the rest of the session or the group finds another way that doesn't involve making the jump check. If they find another way, then then jump check was unimportant and it doesn't matter if everyone made it.
If everyone has to impress the king or they won't be allowed to go on the mission, anyone who fails either has to roll up a new character, sit there being bored, or the DM finds a way to involve him despite the fact that he failed. In which case the failure doesn't mean anything.
The thing about these situations is that parties avoid putting themselves into them as well. If the Rogue has a -2 jump check and the party comes to a 20 foot wide pit, no one is going to suggest that they all jump across. The Rogue is going to fail for sure. The only options are to leave him behind or find a way that doesn't involve jumping. Very few groups are going to opt for a solution that involves one person not playing for a while.
Or what about those rare instances where the +14 rogue doesn't want to help the party, and they need to fall back on the next guy. Who succeeds and how is often very important to story, and creating texture in the party.
There certainly ARE circumstances that are exceptions. I'm not disagreeing with that. It's just that the exceptions are so rare as to prove the rule. It heavily depends on how your DM plans his/her game, I think. Most published adventures, RPGA adventures and homebrew adventures written without specifically being tailored to the group can't really plan the adventure around WHO succeeds.
When they are being written, they normally are in this format:
The innkeeper knows about the cultists' plan, but he is being threatened by them. He can be persuaded to tell the PCs, however, with a DC 20 Diplomacy or Intimidate check.
In practice, this is normally run like this:
Innkeeper: (fearfully) "Sorry, I know nothing about the cultists. Please, just go away."
Players: "Alright, who has the best Diplomacy? The Cleric? Ok, maybe you should try to convince him to change his mind."
Cleric: "Please, we won't hurt you. We'll make sure no one harms you, but we need to find out where they are."
DM: "Make a Diplomacy check."
Cleric: "I have +20, I rolled a 15 for 35."
DM: "He tells you that the Cultists are hiding out in his cellar."
That is pretty much how 95% of all skill checks are handled in games I've been in. In this situation, it simply doesn't matter that the Rogue has a +2 to Diplomacy. It also doesn't matter if you are running the game in 4e or 3.5e, the game works exactly the same. Except the DC in the 4e game is 25 and the Rogue has +15, meaning the Cleric needs a 5 and the Rogue needs a 10. Which means they both have a chance of succeeding and the Rogue can role play his outgoing character without fear that he's screwed over the party by opening his mouth. Even though it might have been better to let the Cleric speak.