Bob Crawford writes:

Table driven models are only "perfect" at the (often very few) points
in the table (and even there depends upon the accuracy of the
measurements). Elsewhere they too are only approximations, the
accuracy of which depends upon how well the real world contour matches
the interpolation method chosen.

They can be made much more accurate than theoretical models, and they are
provably accurate with respect to the real aircraft at demonstrable points,
which is useful for certification.