Maybe a casual user doesn't care, but a power user / dev trying to script it would benefit. Just like how some users of Linux applications just use them interactively and read the English language stderr stream, while others appreciate a myriad of exit codes so a calling script can unambiguously do different things depending on what sort of problem the application is presenting.
Well, the exit codes of both of those commands (despite being different) is actually 7. But 7 does not match either error string, so the power user would have to string search it anyway.
eclipse ~ # route add 1234
SIOCADDRT: No such device
eclipse ~ # echo $?
7
eclipse ~ # route del 1234
SIOCDELRT: No such process
eclipse ~ # echo $?
7
Maybe I used a bad example? I get your point though.
