I recently finished a contract at lockheed. We insisted on 100% code coverage. It was not that hard to do, and improved the code quite a lot.
At our first integration meeting everything worked on the first try
As we discussed, that, of course, depends on how your business use-cases are arranged and implemented.... and also, in our case, the proper use of Mocks for such things as FTP and DB performants. Also, since we have external groups we interface with (such as Enterprise Transport, which sends to external entities) we need them to stand Mocks up too. Lots of moving parts. We're only required by Enterprise to have 80% code coverage on new code, and rightfully so.
In an ideal world, sure, 100% is best, but we've done well at 80%.
My biggest real complaint is the requirement we mitigate all Criticals, Majors, and Mediums in SonarQube. SonarQube sometimes has some pretty stupid code-quality conclusions.