How much influence do freelancers have in determining what payroll software their clients or companies they work with use?

The influence is actually coming from the companies. 

We win in the marketplace because of our beautiful end user experience. The companies that are a good fit for Wingspan want to invest in their teams because they depend on contractors. These companies don’t have a thousand employees and then two contractors that they can just pay through Chase. And they realize that, especially in the talent marketplace right now, there's too many options for individuals—any way that they can invest in those folks will help them recruit and retain talent.