If someone wants to jump into a cavern and use strength to flap his arms to fly, rolling a d20 can be to see how much the person fucked up. A 20 isn't an automatic success.
Same when someone mixes a potion, the d20 may be to see how much it will poison the creator if they drink it.
Roll to see how badly you fail.
Imagine how angry gop would be if the democrats would do this...