The square on the hypotenuse...

On a recent family holiday, I spent a lot of time teaching one of my granddaughters how to solve quadratic equations (I had to mug up on it first!). And I thought to myself - what's the point?  In my long life I have never, outside the schoolroom, had cause to solve a quadratic equation - nor have I ever needed to use Pythagoras's theorem or trigonometry.  So why on earth do we bother to teach children these things?  Unless they specifically want to specialise in maths, or some science subject which will require advanced calculation, all a child needs to know to get by in life is the ability to add, subtract, divide and multiply, and perhaps, just perhaps how to set up and manipulate a basic algebraic equation.  Are we wasting our time - and theirs?