Because you store that as well for "data science".
if a data scientist thinks that data is even remotely accurate they should not be a data scientist.
I'd be curious to see how the distribution compares between birth records and agegates.
I expect an oversaturation of dates like 1/1/80. Hell, I guess we can use 9/9/99 now too.
I seem to recall Steam publishing something like that a while back. A huge fraction of their user base was born on January 1st ;)
That may at least partially be because the year is the only part of the birth date you enter that's saved for the next time Steam shows you an age gate. I've tried to change it back to the correct month and day a few times over the years, but next time it will default back to year-01-01.