If your damping factor is the minimum necessary of say 10, and then you use DSP to tailor the measured frequency response to whatever curve takes your fancy, does it even matter?
Given that the result of low damping factor / high output impedance is just a (small) change in frequency response, it is completely fixable by EQ.
However, to do a precise EQ correction you would first need to measure the amplifier output when driving a specific loudspeaker load - and I suspect this would not be trivial for most (non-technical) people. Also, the required EQ correction changes with any new set of loudspeakers you connect to the amp.
Of course, given that the change in FR due to low damping factor / high output impedance is normally small, and variability is mainly located in the LF range, it is usually swamped by room effects, and consequently implicitly taken care of by room EQ.
While I personally like to see amps that have very low output impedance, in my experience this is a relatively secondary issue in most cases - it is more important to have enough clean power. Thankfully these days you don't really have to choose one or the other, as most good amps also have low output impedance.