Why does K3 reporting only deal with foreign income?

The sole purpose of Schedule K-3 is to report foreign income in great detail.

Many of US partnerships and S-Corporations are required to file this form, but without any foreign partners or transactions, the form is almost completely blank for them. 

The IRS says you must complete Part II and III even if you have no foreign income or transactions.

On the K-1, Box 16 is checked.  Do I uncheck it because there is no foreign data reported on the K-3.

Thanks,

John K.