I don't know if the article talks about this or not (paywalled), but my guess would be due to public distrust. In case you weren't aware, 23andme was recently hacked, exposing 6.9 million users data [1] and a class action lawsuit followed [2].
My personal biggest issue has always been with their TOS regarding how they forever own and will retain the rights to the provided DNA sample and resulting data derived from your DNA. This data was not treated or regulated as sensive medical data under something like HIPAA, so who knows how well they safeguard it [3].
Their website claims they won't sell the data to 3rd parties or insurance companies without users consent, but we all have heard that before from Silicon Valley companies. This data could be sold or used in the future in ways I cannot fully conceive right now, and/or in ways I don't agree with. With the rise in popularity of things like GPT, who knows if they will use the data for training AI models. These problems aren't unique to 23andme, rather any of the tech DNA/ancestry companies.