Re:Go do something else, maybe (Score 1)

Automata theory is fun.

It is also useful. In your digital systems class you were designing finite sate automata. It seems to me to be really useful to know what sort of things you can make such a thing do. When you start asking these questions you are doing automata theory.

Regular expressions are a nice way to represent a language accepted by a finite state machine. they are used for pattern matching and parsing text (this is useful whnever you want to search for anything

if you combine regular languages with more powerful systems you can do neat things like code generation, write compilers, and (try) to make systems that understand natural language.

The theory is useful when you want to know what your machine can do.