[souffle]

Yes there are plenty being bred and yes many of them do have good lives without problems but there are many many also that do have issues and many many that go unrecorded as having problems. They exist because people found out that hey it is possible to mix these two species and you get a variety of colours that make them more appealing to the pet market than the plain old brown things! Most hybrid animals like mules or ligers are infertile however somehow the dwarfs slipped through that net and they can actually breed so people just kept doing it and the market is there so they will continue to do so.
Small animals like these are inexpensive and sad though it is many owners who have one who becomes sick do not take it to the vets so genetic illnesses are not reported as frequently as they might. People eventually come to assume that they 'only have a short life' and are easily replaced for a few pounds rather than going and spending a lot on a vet bill for treatment.
The genetic pool in dwarves is quite small however it is also quite robust so a level of inbreeding in pure bred hamsters can be quite high however these animals are also monitored by the breeders and they would immediately stop a line showing evidence of any genetically inherited diseases. There are also wild caughts being introduced to widen the genetic pool in many countries.
The rodent farms will not be interested in this and ship them out at six weeks with no idea of how they fare and what happens to the lines and if they are throwing up ill hamsters and so it continues. I am glad that you appreciate the importance of breeding ethically.
I wouldn't let them have play dates. This is something that will stress them particularly the male and a constant 'dangling a carrot' in front of him will cause the release of stress hormones which have the same effect as stress in humans. It can shorten their lives. It makes them constantly search for the mate and try and escape. If they never meet they do get used to the scent of each other in the air and stop fretting. They can also be very quick to sneak in a mating which could result in pregnancy.