Note that this is the initial selection of orbitals. The "real"[1] orbitals are linear combinations of them. In some cases it's good enough to mix them using some easy combinations like in https://en.wikipedia.org/wiki/Orbital_hybridisation but in the general cases you must use a computer to calculate the best combination https://en.wikipedia.org/wiki/Hartree%E2%80%93Fock_method .

[1] It get's more complicated.

There's nothing particularly special about them, and they fail to be a good basis set for solutions of other types of quantum systems. Conversely, they can be useful for non-quantum systems - any sort of wave equation in a sphere.

It's not an intrinsically quantum mechanical thing.