If there are six people waiting on the latecomers, that's 10 minutes times 6. Sixty minutes. One hour of collective wasted time.
If you hold a lot of meetings that each start late, the wasted time will really add up.
So, start your meetings on time. It won't take long before the habitual latecomers will start coming on time, particularly if you start your meetings with a piece of really important news that your employees would much prefer to hear first-hand.