[pessimizer]

Why would you explain classical mechanics at all? It's an inaccurate simplification.

[pdonis]

It's much simpler to compute answers with classical mechanics, and the answers are accurate enough for many practical purposes. As the saying goes, all models are wrong but some are useful.

[kortilla]

Classical mechanics covers the vast majority of the interactions in day to day life people will have. There is a reason it’s “classical mechanics”.