Do I need an inner tube on a tubeless motorcycle tire?

I pretty much know nothing about tires. I have tubeless tires on my 99 Yamaha V-Star 650. The mechanic mentioned to me that I should get tubes to put in the tires. So, how does that work? Would one just remove the valve stem and place a tube inside of the tire? I just thought it was odd the mechanic told me that I should have tubes in my tires. Thanks! Jack