I recently (successfully) applied for a job at a fashion company, doing technical back-end stuff. My invitation to interview said "just wear what you're comfortable in". On the basis that they probably didn't want me turning up in my underpants and slippers I wore a suit.

I've always considered the business attire interview convention to be a very useful protocol, and actually found it a bit discourteous when they tried to take it away from me. Business attire might be considered conventionally high status, but it also sets a bounded limit on how good or bad applicants can look. If they're going to be judged based on their clothing, at least they're being judged on a scale which is common knowledge. Once you remove that protocol, you have no idea what you're competing against.

I actually asked the panel interviewing me what they all wore to their interviews with the company, and every one of them went for formal business attire.