Comment by Brybry

The reason given that the SSA does not clean up the data is it would cost too much for little to no administrative benefit. They also don't want to add new inaccurate data to the system.

The no administrative benefit bit checks out with napkin math. Of the 18.9 million entries for people age 100 or older they are paying out benefits to 44,000. The total number of people in the US age 100 or older is around 90k to 100k, depending on time period for comparison.

There's an Inspector General audit report in a nearby comment for source.