The hyphens make clear that you are using a compound adjective. In fact, a common error in writing is omitting hyphens when they are necessary. For example, someone writing I saw a man eating alligator probably meant I saw a man-eating alligator .
This, this and this.
Awhile ago, we saw a story on this site about a chocolate printer. Of course this was actually a chocolate-printer, a device that prints using chocolate. However, without the hyphen, it refers to a printer that is made out of chocolate. Without the hyphen, what are we to make of The Chocolate Lover's Cookbook?
Hyphens are also important when one needs to disambiguate between compound adjectives and compound nouns. What's a high school building? A building that's a high school (a high-school building) or a school building that is high (a high school-building)?
Hyphens are just another example of how we treat punctuation marks as though they were boogers, something to be expunged and discarded, kept away from ourselves and others. But without them, we cannot distinguish a panda bear who eats shoots and leaves from a mob hit-man who eats, shoots and leaves.