The idea comes from Basic Fantasy RPG's optional rules section. It uses a simple table for ability check DC's that applies over all levels. The specific math doesn't matter for the sake of discussion, but if you want to know, it looks like this:
Character Level Ability Check DC
The assumption here is that a DC's static value doesn't change with the task being attempted, but rather with character level. Characters will get better at doing things as they level up. Much better in the long run, but that covers all twenty levels, so it isn't very dramatic from one level to the next. BFRPG only suggests it for ability checks. I would add skill checks to this as well, just to make things as cohesive and simple as possible.
So, climbing that sheer cliff becomes easier and easier as you level up. And the same goes for smithing that cool sword, or tracking those goblins through the woods.
I've come to love the advantage/disadvantage rule from D&D 5th as a way of quickly and easily adjudicating whether something is easier or harder than usual. That combined with this DC list is actually a very nice way of determining the target number for anything outside of combat.
I guess what I'm getting at in this post and that other post from a while ago is that if you have numbers simultaneously going up on BOTH sides of the equation, then you are doing yourself and your system a disservice.
Think about it: A level 1 rogue in D&D 3.5 has roughly a +5 to lock-picking, and comes across DC 20 locks in all his dungeon exploits. That's a target number of 15 on the d20, or 30% chance of success. Then that rogue levels up and up and up and gets to level 10. Since he's been putting ranks in lock-picking a bunch, his bonus to that is now +15. But all the locks he comes across are now DC 30. So what is the target number on the d20? Still 15! That means this rogue still only has a 30% chance of picking the locks he comes across.
In fact, this was even more egregious in the DMG for 3.5 and 4th edition D&D, where the authors gave you a table for appropriate DCs for things as the characters leveled up, which got harder instead of easier for the same tasks and checks. So climbing a rock wall for level 1 characters was a DC 15 climb check, and THE SAME ROCK WALL for level 20 characters was a DC 25 climb check.
I'd go so far as to say that this encourages bad DMing habits. After all, if locks keep getting harder and harder to pick, then simple locked doors are as appropriate a challenge for level 10 characters as they are for level 1 characters, right?
WRONG! If your level 10 characters are still sneaking up to doors in dungeons and banking on a good roll to pick a lock without alerting wandering monsters, then you haven't delved into the true potential that is high level RPG play.
That level 10 rogue should be able to pick that lock no problem (or at least with much LESS problem than his level 1 self). But that shouldn't be all he has to do. This time around, there is an encounter going on in the room that the rest of the party is trying to shield him from, and the walls are slowly closing in so time is an issue, and there's contact poison on the doorknob so a failed check results in paralysis.
THAT'S the difference between the locked doors in front of a level 1 rogue and a level 10 rogue.