It's not nessesary to use those words, but they do make certain expressions seem stronger. It's one thing to say "that movie was really scary" and it's a whole other thing to say "I was shitting my pants from begining to the end". See? It's a whole another level of fear.
I do use all of the above words, not because I can't explain myself without them, but because sometimes you just need that oomph that you can't get without using them.