I find it particularly useful when I would need to look up lots of library functions I don't remember. For example, in python I recently did something (just looked it up:

    for ever my file in directory 'd' ending '.capture':
        Read file
        Split every line into A=B:C
        Make a dictionary send A to [B,C]
   Return a list of pairs [filename, dict from filename]

Same when you a few times per year need to write some short bash script. It's really nice to not have to remember how it really works again!