It has just occurred to me than the real value of projects like Greasemonkey and even very quick-to-prototype languages like Python and Ruby is that they let you fix things that bug you really really quickly and with relatively little effort.

There are so many things that people put up with, just because they figure “Well, it’s just this once”. Doing it manually THIS TIME is better than spending the time making a generic tool that can fix the problem every time. Abstractions are a bit of a bitch, after all. There are different levels of this, largely depending on computer ability: CS students are more likely to write a quick script to automate ordering pizza than for instance management students (who would set up a committee to discuss the possibility of getting an assistant to do their pizza ordering).

With scripting languages, you can get a quick-and-dirty one-off solution in a very short amount of time. No need to generalise and a lot of time saved overall.