These people were, for example, officials and priests (insofar as they had to be able to read rituals and other sacred texts), as well as craftsmen whose work included the making of inscriptions.
The prerequisite of every writing system is a basic standardization, but such a standardization is not equivalent to a canon (an established body of rules and principles) in the degree of stylistic conformity that it requires.
A recognized canon of Egyptian hieroglyphic writing arose in the 3rd dynasty and was maintained until the end of the use of the script.
There was no lack of attempts to replace the hieroglyphic writing, cumbersome and ever more divergent from the spoken language, with the simpler and more convenient Greek script.
Such experiments, however, remained ineffective precisely because of the emotional value that the old writing system had when the country was under the foreign domination of the Macedonian Greeks and the Romans.