Hussar
Legend
Sorry. Nope. That's not how they work.It doesn't. It however should aim to reflect the reality of the fiction it is depicting, and presumably in the fiction some things are more difficult than others. Granted, as taking account everything is impossible, simulation can be simplified. However, not taking into account a major factor like this definitely makes it weaker simulation than one that takes it into account.
All of these games set the DC (or equivalent) by the difficulty of the task in the fiction. If you are not doing it that way, then you are simply doing it wrong, which is what breaks the simulation.
The DC is set by the skill of the character. Not by the task. It might be modified by the task, but, generally it isn't. If you are setting the DC by the task in GURPS, you are not playing the game as it is meant to be played. Same with early era D&D. The chance of the thief to open that lock is set by the level of the thief, NOT by any external factor. That's why retries are not allowed.