It is a bit worse than I at first thought. I ran some very simple SPICE models on pickups, pots and cables. The simulations assume a 500K volume pot (typical) and 15' of high quality (Belden 8410) audio cable.
The graph below shows a simple model that includes only the effect of a pot. As you can see, the gain is reasonably flat to 1 kHz, then drops dramatically.
When you include the coil self-inductance (on the order of 3 H - though actually this is conservatively low...) The effects of the volume control on the brightness of the instrument are dramatic. The first plot shows the frequency response of the system with the volume high (about 95% of maximum). The most striking effect is that the large inductance of the coil adds a very sharp peak at about 4 kHz. This is no doubt well known to the manufacturers.
Finally, when you put this pickup, (i.e. the inductance as modeled) in front of a volume pedal, at about half volume, this is the response that you get.
Notice that all of those highs are completely lost - we are talking more than 10 dB (10 fold) signal loss) in a highly audible portion of the signal range.
An impedance mataching circuit will only get you part way there, as the effects shown in the first plot will go uncorrected. You will still get the brightness peak, but it will be much attenuated.
One thing this exercise has taught me is that the actual guitar cable is a big deal. Belden 8410 is unusually good stuff - better, I think, than you can expect in many commercial cables - I have seen 100 pF/foot often. Changing the length from 15 to 6 feet can mean the difference between having nice brilliant highs and having weak signal from the 24th fret.
I hope this helps.