1. Because those embryos are going to die even if all embryonic stem cell research stops today. You really think it is better that they get incinerated as biowaste, meaning nothing to no one?
2. Because you wouldnt expect cures at this point. It took adult stem cells over 50 years to produce a single cure in a single patient. I am NOT against adult stem cells, they saved my life. But what I know after going through that transplant, is that 50 years after that single treatment in a single patient, its not advanced enough to abandon all other means of research. A bone marrow transplant is THE number one stem cell treatment, and really the only one on the approved public market. Mine was 4 years ago. It is still so risky that it has a near 50% fatality rate. Matching is so stringent, that over 2/3s of the people who need it, cant get one because they dont have a donor and cant use their own stem cells. Because the transplant is so expensive that between 1/3-2/3s of the people who have a match cant afford to go through it. 100 years of adult stem cell research, the single treatment that accounts for 95% of the diseases treatable by adult stem cells, still has the stats I described. And they still cant do it without high dose chemo and radiation, which puts me at risk for at least a dozen cancers, including the very same type I had the transplant for, in addition to making me infertile at 23 years old. The chemo and rad is also partly responsible for the high fatality rate. They have to kill your existing bone marrow and all white blood cells - you have literally no immune system for a couple of weeks, and many people end up with fatal infections at that point. The rest of the fatality rate would be due to rejection, which happens even in perfectly matched cases. The risks are reduced if using your own stem cells, but it can still happen.
I am thankful for my life, but do NOT consider that a good enough reason to abandon other forms of research.
3. Remember, if they had stopped adult stem cell research after 20-25 years in the lab with no cures, we wouldnt have adult stem cell treatments at all.
4. Again, the embryos die regardless. I think its better they die being used for something important, rather than, oh, well, mommy is done with ivf so we're just gonna incinerate you. I support embryo donation, but few choose to do so, because lets face it, ivf is for vanity pregnancies, not people looking to be parents. These are people with enough money, or good enough insurance, to go through thousands and thousands of dollars to screen out embryos, create designer babies, and have their own biological children rather than adopting kids who already dont have parents.