Thanks to Ben Kovitz who, in Q: "gerund + genitive" vs "gerund+accusative" ("scribendo epistulas" vs "scribendo epistularum"), pointed out Cicero's referring to himself in the first-person plural, in the following:
"...[ ]...ut stante re publica facere "solebamus", in agendo plus quam in scribendo operae "poneremus"...[ ]...sed actiones nostras "mandaremus", ut saepe "fecimus";
which is well-translated in Ben's answer.
Here, in contemporary society, only The Queen refers to herself as "We"; it is a part of Her status, as The Queen.
Decades ago the then Prime Minister, the late Margaret Thatcher said: "We have become a grandmother.". It triggered waves of mockery, ridicule and just laughter. If any Englishman/ Brit referred to themselves as "we" people, at the very least, would look askance, laugh; or, a sarcastic--who do you think you are--the word "idiot" (or worse) either implied by vocal-tone or stated.
Clearly, Cicero was living in a different time/ place and was highly respected (as was Thatcher--even by those who despised her) but "we"--why would Cicero have done this; what effect would it have had upon his audience?