Question about polarity-inverting preamps

I read somewhere that some preamps invert because it eliminates the implementation of another stage for the signal to pass thru. Maybe someone knows why this inversion occurs in the first place? The designers avoid the issue by having the accompanying model power amp invert too. Some preamps do offer polarity switches.

Here's some food for thought... in a single ended system the preamp's input signal is configured as a positive and a ground. To process the signal the preamp can only work with the whole wave, both positive and negative. So out of necessity the preamp inverts the incoming positive to generate the missing or negative half. To make the output useful at the single ended connector the processed wave must again become single ended, that is, split. Whether the positive or negative becomes 'the signal' appears to be arbitrary. My uninformed guess as to why the output remains inverted is that the inverter plays a part in the splitting process. Who really knows why?