Inspiration - Stylish Eve via Pinterest
My job being in the tech industry (and often working remote) allows for me to dress about as casual as business casual decency allows. But for those occasions when I travel to meet a new client, have a big presentation with a high-level boss or in times that I have had job interviews - I think having a basic, great fitting suit* is critical. It immediately shows whomever you are meeting with that you consider meeting with them important enough to put your most professional foot forward. Which I think implies you care are about the meeting, that you are likely conscientious, likely hardworking, likely organized and likely to do a good job. All great things to project in a first impression.
(*This is my friend wearing my suit - I think if this suit actually belonged to her it could use a touch of tailoring in both the jacket sleeve length and the fit of the skirt.)