The point is more that before computers, you could at least make a somewhat reasonable claim that it's useful to know the formula in case you need to solve a quadratic - even if you don't understand the formula.

But nowadays, you can just feed the equation to Wolfram|Alpha (or Sage, or Mathematica, ...), so there is no point in blindly memorising formulas.

And I don't think I've ever had a formula sheet in one of my maths exams in school...