Might be needed if your salary expense has to be charged back to various internal accounts or to external clients. My first job was salaried, but I had to fill out a time sheet so clients could be billed.
I don't even fill out a timesheet; they just pay me. It was kind of shocking at first when my manager told me there wouldn't be any sort of time tracking.
In my case, the company uses a single time tracking system for all full-time employees across the country. Different states have different requirements for reporting. There are seven types of PTO, depending on where the employee lives.