Minifying improves performance for your page overall by reduced file-size (it removes comments and unnecessary white-spaces), so your script loads faster and it is parsed faster, since comments and white-spaces don't have to explicitly ignored
Minifying means that there is less text to parse and variables take up less memory (and are quicker to compare, hash etc) so there can be a considerable improvement in both speed and memory usage - escpecially important on constrained devices