That's the "Idaho stop". You're moving at speeds slow enough to be easily able to check for traffic without stopping, plus losing inertia as a cyclist is much more annoying (and arguably even dangerous) than for a car.
From a driver's perspective, you don't want to wait an extra 5-10 seconds because now the bike in front of you has to get back up to speed. 0-5mph is the slowest change and the most energy
