Almost any job ad on any job site includes a mention about required previous experience: "The ideal candidate will have 5 years of experience in a similar role", "We are looking for someone with 3-5 years related experience", "At least 7 years of experience performing similar tasks is required", and so on.
Anyone who has ever hired a new employee in their team knows how difficult finding the right person can be. Not only does the newcomer need to meet the technical requirements of the role but they also need to fit in your company culture and get along with the rest of the team. Indeed, finding the right candidate takes time and costs money to your organization.
Anyone who has ever posted a job advertisement knows that the majority of the received applications are not going to fit the role. Some are too junior, some way too senior, some don't mention the basic skills required for the job, and some don't meet any standards of a well-written job application. Also, if you have ever done this, you know how extremely time-consuming it is to screen 200+ applications.
Have you ever interviewed someone who seemed like the perfect fit for the job on paper but during the interview, you just didn't have the "feeling" with them? Maybe the candidate did everything right during the hiring process but your gut was telling you that something was off?
Company culture is the combination of the shared values and behavior of the people working for the company. Some company cultures are intentionally built and others have developed on their own. The latter is especially the case in start-ups where the culture is often very closely attached to the character of the founder(s).