If you’re working with strings in any capacity at all (and what developer isn’t), it’s hard to deny the flexibility of regular expressions. Why use complex parsing code to process a string when you can do the same thing in a concise, 20 character regex pattern? And if you put that same pattern in a .config file, you can change the behavior of your app without recompiling. It’s less code doing more work.
Mark Nutter’s RegEx Explained is a great introduction to the use of Regular Expressions in REALbasic.