Uhh, master cylinder failing would result in all brakes failing. Things these days are internally partitioned so that front and back are separated, and thus complete failure is unlikely, but still possible. It used to be all in one, and the e-brake is very, very important in vintage cars because of it. Less so now, but there was no good reason to change it besides manufacturing cost.
You’re making an awful lot of assumptions on my driving skill based on (checks notes) wanting a redundant system.
If this is your version of “impersonal”, you need to recalibrate.
And no, I’m not wrong. Total brake failure still happens, and a separate system is still important.