Out of habit, mostly. For most users, the privacy issue that people scream to the top of their lungs on this forum isn't given a second thought. Or, they frankly don't care enough about it. Safari is a good browser, but some websites weren't built for Safari. Education websites don't run nicely on WebKit. Yes, Chrome does use more battery, but most people bring their chargers with them anyways, so if they do run out of battery, it's easy enough to find an outlet. I like uBlock Origin, which isn't available on Safari. Now, the reason why people would instead use Chrome over Firefox is because of the first reason, it's out of pure habit and what people are used to. Firefox and Chrome, in my experience, use the same amount of battery. Firefox may have a slight edge. Most of the services I use are Google Services, so why not just the same browser that makes those services?