Because 23andMe can't run a disclaimer like that without being either:
- totally disingenuous
- defeating the core marketing angle of their product
Either they are issuing the disclaimer in good faith, in which case their marketing becomes "we don't really know for sure, this is just a for-fun thing, do not base any health decisions off this". This is antithetical to what 23andMe is trying to do.
Or they issue the disclaimer in bad faith - i.e., they claim certainty in their information, they claim reliability, and they market the product as a medical tool, and then slap a shitty disclaimer on the bottom like the small-print of a crappy infomercial purely for legal reasons.
The latter approach is just creative mislabeling, like calling vibrators massagers.