"Why doesn't the loss on a final 1041 estate return show up on the K-1?"
This is a typical TurboTax issue; losses do not automatically flow through to the K-1(s). Following the steps below should result in the loss appearing on your K-1(s).
Under FEDERAL TAXES>>Distributions enter the amount distributed to each beneficiary as a negative number (see first screenshot).
Enter Forms Mode (click the icon in the upper right side of the screen) and open a K-1 under Forms in My Return (see second screenshot).
In the Beneficiary's Allocation Smart Worksheet section, enter the beneficiary's percentage of the income distribution deduction (see third screenshot) and repeat, of course, if you have more than one beneficiary.
You should now see the figure(s) appear on the appropriate lines of your K-1(s).