I see that as poor framing of a challenge. If the challenge is something you can overcome with just, say, convincing a single person, it probably shouldn't even be a skill challenge. Not all skill checks are supposed to be part of a skill challenge, and Rules Compendium has examples of skills in play where skill challenges are not involved. I do know what you're talking about, and the issue is using a skill challenge where one doesn't need to be added. Or sometimes players come up with a very creative solution and you just bypass the skill challenge, the same way you would let them bypass a fight thanks to a particularly creative idea. If the skill challenge was intended to be long, like 8 or more successes, and the players still came up with something that bypasses the entire thing, then that would just be bad framing (like requiring 8 successes to get through the gates of a city).
According to the rules in the 4E DMG, you had to have anywhere from 4 successes before 2 failures to 12 successes before 6 failures based on difficulty. Throw in initiative and explicitly telling people they were in a skill challenge. Once you were in the challenge the numbers were set.
Maybe you didn't run it that way and I certainly wouldn't run skill challenges that way any more. It's not like I didn't try to make skill challenges interesting but if you ran them as described by the rules they were a sequence of die rolls with boxed text that made little difference. I liked the concept, the implementation didn't work for me. I think it was another example of the original books being pushed out too soon, the compendium had more of what it could have been if given time but it was too little too late.
So now in 5E I may use a similar structure occasionally but what the people say and do matters. It may be a situation where I want the players to use a variety of skills but I never have a set number in mind. Instead, I advance the scenario as it make sense based on what they do and the successes or failures along the way.