[User23]

The US Census is public record and breaks down all kinds of demographic information by zip code. The USPS is almost certainly just using census data. Even if they didn't provide the convenience, a marketer could easily replicate what they currently do.

If you have a problem with the US Census Bureau collecting demographic data or making it public, those are certainly valid positions to hold. However, point your ire at the right target.

[edf13]

You haven’t answered my point as to why the USPS needs this extra info to do their job?

[User23]

Because I thought that was self-explanatory: part of their job is selling advertising. Cash is tight enough at the post office as is. Why let third party marketers sell advertisers public census data instead of just providing it directly?