In the hog dog world we see a lot of crossbred dogs, but with bird dogs it doesn't seem to be as common. Why is that?

bird dogs have been breed alot longer than Hog Dogs,
there is pictures of Vizslas in the Hungarian Noble courts from 800 ad, Pointers and setters go back into the 1850's. I know from personal experience that getting a well bred bird dog increases the chance of getting a good dog tremendously. You can look at the breed standards and get a pup from good hunting stock with a much better chance of getting the type of dog that you are looking for. Most Pointers and Setters have been line-bred for several generations to fix type. I think everybody with hog dogs is still looking for the type of dog they want. I might be wrong. Just my 2 cents.