+1, I'm not sure what understanding the order of operations gets you outside of the 3rd grade. I am not making the argument that most people are smart but I would say that useless information is just that...
It is easy to refer to math without realizing you are doing it. In trying to make
sense of our experience, we all routinely make judgments as to whether events
are related. We make assertions like "That just couldn't be a coincidence."
Like it or not, such judgments entail math. Probability and statistics are
highly useful mathematics (and not widely enough taught in my opinion).
As to why it matters to know the order of operations, that is part of the language
of math, and math is involved in so many parts of life that you really have to be
incurious to not want to be able to read the language of mathematics.
In the 20th century, a guy you've heard of discovered a remarkable relationship
between mass and energy; we learned, for example, that a clock gets heavier
when you wind it. If you don't know the order of operations you don't know
how to read E=mc².