Many people using Mac will use safari because it's power usage is incredibly low compared to the others. Im a Firefox user, but on a MacBook, safari is the only option.
Swapping out one app for another that's almost identical but with less CPU usage seems like a no-brainer. Though I do keep Chrome around with a couple tabs open for its development tools during work.
Safari even uses fewer resources when watching Youtube/Netflix at the same resolution. I first noticed this while using a dual monitor setup with a fullscreen game on one and Youtube/Netflix on the other. I noticed my game's FPS would improve if I merely changed from Chrome to Safari when watching video. Did some more scientific measurements and never looked back.
Firefox is nice and chrome is ok but they're a distant second at the moment due to the ecosystem with iOS