Batch Renaming Shouldn't Be a Hidden AppleScript

So I'm needing to change the file extension within the filename of a bunch of JPEGs in OS X. This is a huge pain, of course; there's no easy way to batch change filenames within the GUI. I start looking up some sort of BSD bash script way to do it, and I found a few before stumbing over this gem of a hint:

Take a look at /Applications/AppleScript/Example Scripts/Finder Scripts. I found a script that will add extensions and prefixes, as well as one that will do wildcard renaming. Very useful!

Yes, very useful. Also useful is writing a script to run in the Terminal.

As IceBurrg pointed out to me, DOS 1.0 had the "ren" command that basically did batch renaming with wildcards. That's great; why didn't that carry over into Windows XP file management GUI or the Mac OS X Finder GUI? It really shouldn't be such a pain in the ass to rename several files, or change extensions.