Businesses can often save money by hiring ICs instead of employees. In addition to salaries or other compensation, employers have to pay additional expenses for employees, like payroll taxes, insurance premiums, and employee benefits. When hiring ICs, you don't have these expenses.
Hiring ICs instead of employees also reduces exposure to some types of lawsuits, such as those alleging job discrimination or wrongful termination.
Most importantly for many employers, ICs provide a level of flexibility that can't be obtained with employees. You can pay an IC to handle a specific task, allowing your business to get specialized expertise for a short period without having to pay for training. Once the IC's job is complete, the contract ends and your business and the IC simply go your separate ways, without any need to terminate employment or think about severance, unemployment, or health insurance continuation.
For more information, see Pros and Cons of Hiring Independent Contractors.