Welll...she is trustworthy, loyal, helpful, friendly, courteous, kind, obedient, cheerful, thrifty, brave, clean, and reverant and would make any boy scout proud!
If this is not enough she is healthy, intellegent and beautiful.
Then just about everyone I know should breed their dog, if that's all you think a dog needs to breed. Heck, why shouldn't I breed my Pom? He's all of those things! And he's also thrifty because he's a little dog! BUT - I'm not going to breed him. Even after he gets flyball and maybe agility titles. He doesn't adhere to the standard. If I bred him, it wouldn't benefit the breed in any way.
Here are some nice white GSDs.
This is Atlas from Atlas Kennels. He is titled out the wazoo.
This male is only 8.5 months old in this photo. Bred by Kerstone shepherds (I know many on here have mixed opinions about this breeder), but I'm not usually a fan of white dogs, and this dog, in my opinion, is stunning.
Here are some GSDs that I'm sure were bred for all of the reasons you stated - look where they ended up. (Each photo is a different dog).
This girl was a drop-dead gorgeous female. You can't really tell from this photo, but seeing her in person (at better angles), you could tell she was a well-bred dog.
I know you might be thinking - but none of those are white GSDs! Trust me - they're just as common in shelters as the blacks, the black/tans, sables, etc. Several of the above dogs were on the euthanasia list. Some were rescued, others weren't as lucky.