It most definitely is affected by the rankings! The ridiculous amounts of yorkies in shelters began when they moved up on the list a few years back. There was always a problem, but that compounded it unbelievably!
As for people gettiing labs.....let me tell you that there are massive amounts of labs in shelters that are being euthanized daily!
German Shepherds not so much, but I just think that is because they do not have the reputation that labs have as being family dogs (even though people have no clue that labs are not good family dogs unless well trained).
Yorkies are small...they are ranked high and many people looking for a small dog want them for that reason....and the greeders are more than happy to place them with them. Does not matter to them that so many will end up homeless in no time.
