To some extent the character set was still evolving, for example the Euro sign was not around until decades later and that would need to be bolted together with backspace characters or escape codes, maybe even downloaded characters, with the printer specific manual (Epson) studied at great length.
In the DOS era (and before with home micros that were programmed in BASIC) it was quite normal to compose things for the printer that you had no expectation of seeing on screen, not that anyone read much on screen (as everyone had vast piles of paper on their desk).
Until quite recently some POS systems were very much tied in to a very specific printer, at least these character sets were a step forward from hard coding a BASIC program to an exact make and model of printer.