1) Portuguese Water Dogs, while more popular than, say, Otterhounds, are NOT an extremely common or popular breed.

2) In my time being involved with shelters, rescue, and dog sports, I've heard of EXACTLY 1 PWD that actually made it in to a shelter. MOST shelters are EAGER to work with breed rescues (look it up, people--breed rescues are organzations of breeders of and lovers of a particular breed who take in, evaluate, care for, and find homes for that particular breed. They do not, as a general rule, have facilities, and exist on volunteer donations and foster homes). A shelter that can get a known purebred into a breed rescue will then have room to save OTHER dogs. The shelters I volunteered at ALWAYS attempted to get hold of breed rescue before making a known purebred available for adoption. The rescues generally deal with fewer dogs, and have better resources for evaluating their breed.

3) PWD rescue is known for being VERY active and pulling their breed from kill shelters/pounds/etc. as soon as they can.

4) They needed a breed that their daughter would be less likely to be allergic to, and they wanted a larger, active breed. PWDs are a good choice, but waiting around for a PWD to show up in a shelter in DC or whatever would have been sorta futile at best, and at WORST might have spurred some idiot or another to get a PWD into a shelter, by hook or by crook. And then sued to get their dog back. Yeah, THAT's a good idea.