How do we know that we have taken all factors into consideration while deriving Coulomb's Law?

It was experimentally deduced that
$$F_e propto q_1q_2$$
$$F_e propto dfrac{1}{R^2}$$
where $F_e$ denotes the electrostatic force between two charged particles with the magnitude of their charges being $q_1$ and $q_2$. The two charged particles are kept apart by a distance of $R$.

Now, from this we can deduce that
$$F_e propto dfrac{q_1q_2}{R^2} implies F_e = K_edfrac{q_1q_2}{R^2}$$
$K_e$ is Coulomb’s constant here and it is equal to $dfrac{1}{4piepsilon_0}$ in SI units, where $epsilon_0$ denotes the permittivity of free space.

Now, how do we know that no factor other than the distance between charges and the magnitude is affecting them? There could be some environmental factor that only has a negligible effect on the electrostatic force but under certain conditions, it might have a large effect on the it under some other conditions and we might just end up ignoring it, right?