Some companies support a business casual work environment yet require professional dress (which I think means a suit and tie) only for candidates during a job interview. Some might say this is in order for the candidate to give a good first impression, but an impression that misrepresents the way the candidate will perform on an average work day is unethical for the candidate and useless for the interviewer. At the same time the fact that the interviewer (or indirectly through his/her recruiters) requires the suit implies that the interviewer is either trying to lie to him/herself about the candidate's true nature, or that he/she is trying to humiliate the candidate, to make the candidate make an extra effort to conform and wear something uncomfortable only to please the interviewer.
No candidate should have to endure this submission, this worship of interviewers as false gods. Outward appearances should not be emphasized over technical or communication abilities, and those who require special dress in order to communicate should not be tolerated in the 21st century. The world is sick. The only way it can get better is by focusing less on the physical and more on the spiritual.
Some might say wearing a suit is not a big deal, and that candidates should simply do it and forget about it. Look at it from the other angle. If it were not a big deal then interviewers would not require it. THEY would not care either way.