There is a popular saying that you should dress the way you want to be addressed. This is to tell us that appearance matters a lot in developing the first impression about someone.
Generally, I would say that physical appearance is vital when considering candidates for hiring. However, this rule shouldn't be cast in stone. It should be flexible depending on the kind of job under consideration.
In the university where I study presently, I have a professor of organic chemistry who is well-known in the field in Nigeria and internationally. He has contributed to the knowledge of organic chemistry in no small measure. If you see this man and you are told that he is a professor, you would argue otherwise. He doesn't appear like someone with a first degree. He wears oversized pants and shirts. The shoes would be like workshop shoes that are nearing their expiration date.
Despite this shabby appearance, he is well sought after in the world of research in his field. Industries hire him to conduct research and give them recommendations. His skill is too vital and needs not to be thrown away based on his poor dress sense. If I were to hire him, I wouldn't judge him based on his physical appearance either. His appearance does not have any implication for the organization or the institution that he is working for. His skill is what is needed. We have many jobs like this.
If I am to interview someone for a job, the kind of job concerned determines my strictness about the physical appearance of the job seeker.
There are some jobs that the mode of appearance is very important to the growth and development of the organization. An example of this is banking. Bankers dress to look presentable to customers. If someone is coming to discuss an investment with a bank representative, it may be counterproductive to appear shabbily for such a discussion. So, my position is that the job under consideration should determine how strict employers would be about appearance. However, one important point to mention is that there are no disadvantages to dressing well to the best of my knowledge.
Irrespective of the job, one should dress well. A few days ago, I noticed the appearance of a young lady undergoing her one-year national service in my organization. She wore a skimpy dress with her navel outside. The dressing falls short of the standard expected around a higher institution of learning. I had to call the attention of the concerned authority to correct her and wear such.
If such a dress is worn to an interview, I am sure that she would be judged according to such an appearance regardless of what she possesses in terms of expertise. One should be careful about how he or she dresses for an interview. The kind of job that you are going for would give you a clue about how the interviewers would place importance on physical appearance.
Where necessary, I am in support of appearance being put into consideration in addition to skills. It shouldn't just be too rigid.