Because now your command isn't /path/ independant. The original assumed you downloaded the patch to your current directory and you can just copy&paste this command. Your example requires me to modify your line making this "process" more error prone.

In that case, their command is exactly as "error prone" to anyone who did not download the patch to the PWD.

You should use && instead of ; but otherwise I wondered the same thing. Useless use of cat, it seems.

Why? How likely is `cd /usr/src` to fail?