> this feels "realistic" because it’s not perfect physics. A perfectly simulated Hooke's law spring
Confused. Perfect physics means perfectly simulating reality, not perfectly simulating an unreal idealized formula. Are you saying Hooke's law doesn't feel realistic or are you saying a simulator for a realistic spring doesn't feel realistic?
And even if you somehow included "everything" with the "perfect" equations, you'll end up with a lot of stuff which does not have a good closed form solution anyways and good luck getting that running (e.g. the dynamics around the air resistance/sound generation) via approximations both accurate enough that it looks better than "faking it" and fast enough that it's actually usable interactively.
This leads to what GP was saying: many just cut things off at "Hooke's law simulates a spring, so I'll use that, but the rest is a bit too much to fit so I won't do it" but "Hooke's law simulates a spring but adding a bit of not-physics based fluff approximates all the rest" actually gives far superior results even though it doesn't only use perfect physics equations as the former did.
In reality, nothing is perfect. Materials are never 100% one material. Rustness is imperfection, the weight and material of the ball, and the place it's attached are also consideration points, how firmly it is attached, and with which material. A "perfect" simulation of the spring itself would have to consider all these variables, and they almost never do.