YMMV, but I've always worked in service-oriented development organizations for startups or companies that behaved like startups on the development side. Pressure comes with the territory and I'd rather know how potential colleagues behave with a small amount of interview pressure before being stuck with a veritable basket case in a real-world high-pressure situation.

I had a guy freak out walking through a simple algorithm in java at the white board in an interview. Maybe he was the best developer ever if he were put in a quiet dark room and never made eye contact with anyone. Given that we had other candidates who could actually interact calmly and intelligently in an interview/collaborative situation, we weren't going to go with the guy that freaked out.