There are several reasons, as far as I am concerned:
Images of code can be very hard to read. EspeciallyEspecially if a person takes a picture with a phone of a screen with a phone. ItIt can be very difficult to cipher one's way through it.
Images of code frequently chop out bits of material. NotNot all terminals have a good wrap function, and even the ones that do can often make it difficult to tell exactly where line ends are.
Images are not searchable. AA picture of code will never be found by others looking for similar problems unless the description is sufficient to match what a future user is searching for.