-v prints non-printing characters in a visible representation. Making strange
characters visible is a genuinely new function, for which no existing program is suitable. (sed -n l,
the closest standard possibility, aborts when given very long input lines, which are more likely to occur in
files containing non-printing characters.) So isn’t it appropriate to add the -v option to cat to make
strange characters visible when a file is printed?
The answer is “No.” Such a modification confuses what cat’s job is concatenating files with
what it happens to do in a common special case showing a file on the terminal. A UNIX program
should do one thing well, and leave unrelated tasks to other programs. cat’s job is to collect the data in
files. Programs that collect data shouldn’t change the data; cat therefore shouldn’t transform its input.
Relevant except below, bolded is the key point.