People are generally not taught how to interview well. To most, it's not a skill to be honed. I find this occurs often in software development, when engineers are asked to participate in the interview process.

This is why you still get companies, who pride themselves on having progressive engineering cultures, defaulting to whiteboard interviews, bland comp sci trivia, and puzzle questions even though they're proven to be awful indicators of on-the-job success.

Ten years ago this is how people were interviewed when they first got into the industry, so that's the only way they know how to interview now, despite the demographic and tooling significantly changing in software development.