I'm sure you're not, but my experience is completely opposite of yours. I'm still relatively early on in my career (I've had 3 software jobs, but have grown up coding since I was 12), but every job I scored was one that didn't use a whiteboard/paper problem during an interview.
I got a lot better at whiteboards with practice; but early on, every whiteboard problem I received resulted in me blanking on even the most basic concepts. I would have no idea how to solve problems on a whiteboard that I explicitly solved in a codebase the week prior. Then I'd step out of the interview and the solution would just hit me.
It's like state-dependent learning, in a way. As I got tested more on whiteboard coding, I figured out that whole problem-solving process better, and I do pretty well on them now. Still, I continue complain about those problems. They feel like a completely foreign, perpendicular challenge compared to having a discussion, answering questions, or writing code to solve the same problem. It's not a skill I've ever used outside of interviews, nor is it a situation that has ever been simulated at any workplace I've been at.
There's nothing wrong with evaluating a candidate's whiteboard presentation skills. If the goal is specifically to evaluate technical or algorithmic knowledge, it's worth taking into account that testing for that knowledge on a whiteboard can introduce a side-effect that bottlenecks the candidate's ability to present their answer.