This question already has an answer here:
Is quantum mechanics similar to Newtonian gravity in respect that it explains how something works but not why it works? Or does Quantum mechanics explain why it works? (I haven't actually studied QM)
Edit: Before Einstein discovered relativity we understood how gravity worked (we could make mathematical predictions with what we knew.) but not why gravity worked (the warping of spacetime) is quantum mechanics similar in this respect, that we know how it works (we can use it to make technology and make mathematical predictions) but we do not understand at the fundemental level, why it works like we do with gravity.