Hiding Unemployment

Col Nathan R. Jessup: You want answers?
Lt Daniel Kaffee: I want the truth.
Col Nathan R. Jessup: You can't handle the truth!
--A Few Good Men

Nice picture (source) of relative difference between "headline" U3 unemployment figure and the U6 estimate that includes various categories of unemployed or part time workers.

Basic rule of thumb is U6 = 2*U3.

Of course, it is plausible that even U6 under-reports true unemployment.

That larger issue aside, the present data arrangement, with all of its issues, still bids the straightforward question: Why don't more people question why U3 instead of U6?