I do it; I like messing with install scripts and optimize them. My next big yak shaving project will be to optimize rkhunter. Did you know it is a 20K line POSIX shell script? I read through it a couple of times, and there's significant potential for improvement both in performance and in its security. For me it's a lot of fun because I like programming in Bourne-derived shells.
I skim little python or bash scripts when I download them. It depends on the project. (I try not to download much source code because this is a pain to do).