Why is it important to look your best and to look professional during an interview?

It is important because you want to look all neat and professional you don't to show up to your interview looking like a sloppy mess or else the person who is interviewing won't like you and thinks you are messy and won't fit in. It is good to have proper etiquette because it makes you look polite and have a good behavior around the people including the interviewer. 
Make sure you are polite and address the interviewer as ma'ma or sir always shake their hands when the interview is done. Always reply to them as yes sir or ma'ma. You want to make a good first impression. 

Hope this helped :)
Have a great day 

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