To make the bussiness profitable. Working without supervision and mostly is honestly.
It depends on what you are applying for, lets assume your going for something to media/marketing,, at that point a normal formal suit isnt your best friend because you must market your marketing skills and it all shows in Personality, Styles/Wear & Professionalism. In other words, wear to impress and add to your creative space & speech.
1- Be direct, do not try to divert topics
2- Never assume
3- When you dont know, you dont know! dont create false loops!
4- Do not wait for questions to be juiced from you, put effort to show knowledge and interest
5- Personality matter, dont be over or under expectations, both are bad just be genuine
6- Accept that some jobs are more suitable for a specific set of personalities due to the nature and goals of the company hiring