You narrate it because it's something the they have declared that they do.
DM: "The wood door has no lock, knob or any other way you can see to open it."
Fighter: "We don't have time for this. I pull out my battle axe and chop my way through the door."
DM: "Okay. The door was pretty sturdy, so it takes you about 15 minutes to chop your way through it...."
It's a waste of time and effort to have the fighter battle a wooden door until he breaks through. The outcome isn't in doubt, so why waste that time?
This depends on the DM. In 5e by RAW, you can keep trying to pick the lock over and over and over, so if there are no time constraints the PC will eventually roll a 20. If the lock has a DC equal or lower to 20 + the bonus of the PC, why waste the time making him roll?
If you've decided not to allow retries, then the roll should happen.