Social expectation is a big part of how a technological society functions. Trains run on time, garbage cans are airtight and emit no odors, and the streets have no trash on them in Stuttgart because people expect things to be that way. If we let innumeracy be acceptable in the US, the quality of our workforce will decline.
Failing to understand that an in-camera DPI of 240 doesn't correlated to a print DPI of 240 is not "innumeracy". It's frankly the logical and intuitive thing to assume.
If one spends zero time thinking about the issue. I'd rather live in a society where people did so and held the bit of knowledge you just related in some esteem. The US is not like that anymore.
