1. The shoot the shit session is guaranteed to be driven by your personal biases.
2. Working on a different ticket with every candidate ensures you can't possibly compare one candidate's performance to another's.
I also send the same screening test depending on role so I do have a baseline, although I'm much more interested in our interaction during the pair session.
[0]: https://news.ycombinator.com/item?id=14570309
1. The shoot the shit session is guaranteed to be driven by your personal biases.
2. Working on a different ticket with every candidate ensures you can't possibly compare one candidate's performance to another's.