Oh no! you wont always be able to make use of the skill. shock and horror. Its not like people get to make use of surprise ending every fight either, but it's an accepted part of the skill.
It may not get used all the time, but in those fights where its relevant, you'll thank yourself for having it. It also frees up a strategy line because you probably wont need one dedicated to getting back up from being prone.
The skill would also mean that you dont have to use dunder if youre terrified about going prone, because falling over isnt the end of the world.