The so-called interview is to look at the resume and then see if this person is really qualified for the job. The use of clothing in various occasions is to convey a feeling to each other. T-shirts and jeans convey that I am a very casual person and will not take care of your face in formal occasions. I'll just have a look at the job. It doesn't matter whether I do it or not. Therefore, people who generally value this job will wear formal clothes. Of course, you don't have to wear suits and shoes for formal wear, but you can also wear business and leisure.