Dressing up is not just for people who want to look good. It can also be away to show other people that you are someone who acts professional in even the slightest sense. The way a person carries himself is not measured just by how he speaks and acts, but also in how he dresses up. This maybe superficial but this is how society sometimes looks at people. For example, two people are applying for the same position, both have identical backgrounds but one wears one of those custom shirts for interviews and another wears jeans and t-shirts. Who do you think would get the job? Dressing up is a way to sell yourself to other people, so if you look good, you would be a lot easier to sell.
With this knowledge, job applicants can give a good impression on the interviewer simply by dressing professionally. Simple coats over a custom dress shirt can already work out for some as long as they carry it properly and with style. An individual does not need to over dress to become more impressive, a simple looking attire that still is professional would already leaps and bounds for the applicant. So next time you go for an interview, try dressing up and see the results for yourself.