I think it will remain uncommon. I agree it would be a good test, but companies and employees alike get very angry when pentesting gets too close to sensitive subjects.

Anyone who fell for it would not only get in trouble for poor security practice, they would reveal that they were job searching. That opens an entire can of worms that creates problems beyond the pentest. This also angers other employees who see it as a double-trap being sprung on employees.

Another major problem is that responsible employees who accept the fake interview but then use their personal laptop to do the interview will have their personal laptop compromised by the pentesters. Responsible testers will immediately abort, but some will try to use the personal laptop to pivot deeper which is a huge ick. It’s also really bad if the company is compromising personal laptops of people who are doing the right thing (switching to personal gear for interviews).

The pentesters wouldn't have to actually pwn a laptop, just getting the employee to download and run anything could go in a report without having the file actually be malicious.