...animal, why should you expect? Why should you expect any less from breeding 2 purebred dogs of different breeds?

There is no guarantee you'll get the best mix of genes.Anyone of the new pups could inherit undesirable genes.All living creatures have recessive genetic material that may stay hidden over generations, then pop up unexpectedly.That's the roll of the genetic dice..

i thought it was kinda obvious that when you cross 2 different breeds of purebred dogs they wouldnt be PUREbred anymore. (since they now have two different breed in them)

Well, in terms of genetics, each chromosome is carrying two alleles, and because the two dogs are different breeds, their alleles for different characteristics such as fur colour, nose shape, eye shape etc, will be different, and when these alleles combine, they will form a new genotype, and most likely a new phenotype as well, meaning their visible characteristics, depending on which alleles combine, and whether they act in a simple dominance/recessiveness, co-dominant, incomplete dominant, or epistatic manner; would influence their characteristics, which could be the same as one parent only (somewhat) or they may be completely different, and a new phenotype would result.

Even if the two dogs you are planning to breed are purebred, the puppies obviously will be mutts if the breeds are different. Not to mention, your female will now be tainted and no longer a pedigree. A female dog can have throwbacks to the litters she has had. Say you have a purebreed Black Lab and you mate her with a Shepard, she can have puppies a few litters down the line that have traits of the Shepard. Unlike in humans if you have a white female that has babies with a black male, if she has babeis with a white male, they'll obviously stay white.