Your first statement isn't quite true. See, for example, https://www.scottaaronson.com/blog/?p=473 https://www.scottaaronson.com/blog/?p=473 In short, it's har

Your first statement isn't quite true. See, for example, https://www.scottaaronson.com/blog/?p=473 https://www.scottaaronson.com/blog/?p=473 In short, it's hard to classically model pretty simple quantum mechanical systems and sample the probability distribution of outcomes. Using a quantum computer to simulate the system and sample the probability distribution is easy.