It's all in the ancestry! That's why there are breeders and then there are Breeders.....Some people who breed pay no attention to a bloodline or characteristics of a dog's ancestors. Then there are breeders whose goal is to breed out tearstain, long snouts, pink points, etc. Many of these are very successful due to hard work and careful attention to detail. Just because you love your Maltese and think she's just adorable doesn't mean she is true to the breed or that her offspring will be true to the breed. Then there is Daddy's side of the family! There is a lot of science to breeding.
This is why puppymills do such damage to purebreeds. They put a lot of animals out in the public with genetic abnormalities, defects and characteristics not to the breed standard. Then someone back-yard breeds their pet and passes on these characteristics and people begin to wonder why a dog doesn't "look like a Maltese" or what a Maltese is really supposed to look like. I am NOT chastising anyone here, just telling it like it is.
I've learned an awful lot since acquiring my precious Pico. And I'm glad I had him neutered at 8 months so as not to be tempted to breed him so I could get pick of litter for putting him out to stud. He has 1/2 pink nose, Microvascular Dysplasia and cottony hair. He's a Love Stud, not a puppy making stud!