Over the course of my career, I've been on numerous interviews. I've interviewed in all kinds of industries. I've never once gone to an interview in anything but a suit. That's one lesson that I learned early on in my career and I've always remembered.... wear a suit to an interview. In fact, I think the rule even goes so far as to say that a woman should wear a skirt suit to a first interview and a pant suit is appropriate for a second interview. It should also be a dark suit.
Well, I cannot tell you how many times I've been in a waiting area and seen another candidate waiting for an interview dressed in something other than a classic suit. I've seen candidates in a skirt and a sweater, or a dress, and even in something that appears to be a makeshift suit. This would be a pair of pants and a blazer that are clearly not part of a suit ensemble. This is usually worn by younger candidates, I would estimate less than 5 years out of undergrad.
If you are interviewing for a job.... whatever job.... you absolutely have to know that first impressions are everything. Your potential employer is going to be looking at the whole package, from how you present yourself to all of your credentials. If you really want that job, start off by showing up in a great suit.
I think sometimes we tend to steer clear of a suit because of the fact that we wear it so infrequently and it can be rather expensive. The cost per wear does not pay off. However, the power that a great suit can have could pay off. Showing up to an interview in a suit that makes you look and feel strong and confident will result in a better interview. You will make a better first impression.
My advice to new grads and those who are looking for a new opportunity... invest in a great suit. Wear it with confidence. Hold your head high! You have a lot to offer... let your style and your clothes help you along the way.