Some things are supposed to be a risk, and they have a chance of failure. But some things are not. What should and shouldn't require a roll is rooted in the effort to bring consistency to a setting.
For example, lifting a gate or heavy object should have no or a limited random element. If you can lift a certain amount of weight, that number doesn't change dramatically.
Same with most professional tasks. If you know how to do something well, then you're going to perform well when you attempt it. Picking a lock? Tying a rope? Deciphering a script? These don't have much of a random element to them.
The d20 system only has one random element for most tasks: the d20. It's a linear form of randomness with a huge range. This is fine in combat and other tasks where using a skill represents taking advantage of an opportunity, but it's terrible for tasks where performance should be more stable. So, for those tasks, something like taking 10 simply works better.
There's a psychology behind the idea of making the players roll, which I fully admit to falling into sometimes. It's the idea that you should never give something to the players. That they need to earn it. That without a risk of failure, success isn't satisfying.
All of these things are true, but the skill system is not the place for this aspect of design. Skills, checks, and DC's are not primarily about providing challenges, they're about describing how characters interact with their environment. The challenges, the risks, and the rewards all belong to design of the environment.
Overcoming those challenges is about the choices you make, not the die results. The risk in breaking down a door doesn't come from the die roll, but from not knowing how strong the door is or what's on the other side. Randomness is used when an aspect of the environment can't be known—when there are no predictable outcomes. They're for the things you might be able to do and the opportunities or threats that might happen.
