For one, one man did, but he was a con artist that made the family hesitant to ever talk to anyone again. When Rebecca Skoot went to interview the family for the book, they accused her of being his crony. It took her 10 years to write this book, partly because it took that long for them to open up to her.

The other half of the reason is that lawyers have, and they've gotten nowhere. There's actually a rather long legal precedent in the U.S. that the tissue taken from a person in the course of a medical treatment doesn't belong to them. It is considered medical waste, and part of the argument is that restricting its usage would hurt medical progress. This is why it is perfectly legal for hospitals to sell the foreskin of circumcised infants to pharmaceutical companies, for instance.