There are a number of benefits to placing a mat under your treadmill, like extending the life of your treadmill, protecting your floors and helping to absorb the impact from running, which will also help to make the treadmill quiet.
While you’re running or doing an interval workout, your treadmill could be inching forward over the surface. A treadmill mat would provide more stability and prevent it from moving.
If you’re leaving your treadmill in one place, the mat will also help to prevent dust from reaching the motor.