Tell that to the engineers working at the LHC and physicists there who hope to develop a standard model beyond our current one that accounts for relativity and quantum physics.
I know. When it's needed, it's really important, and way hard. In most fields of work though, complicated math like that isn't neccessary. And, I know this isn't an equation, but I don't think anyone will ever need to prove, that triangle ABC is congruent to triangle DEF, and not be allowed to use measuring tools, forcing them to try to remember what the heck a "subtraction postulate" is.