Not everyone needs (or wants) a beta. If course, there are varying levels of beta work as well. Sometimes it's everything from a line by line grammar check to the flow of the story; sometimes there's only one part the author wants opinions/help on; sometimes it's just a general read-through to see if the whole things seems to hang right. So it's basically a second set of eyes on whatever the author is looking for. Some need it, some want it, some are fine without it. :)