Battery life - what am I missing?

I've been considering buying an Apple Watch for some time now, but the big sticking point for me is the battery life. With the claimed battery life of 18 hours I can't even plan to charge consistently at the same time every day (e.g. before bed, while getting ready for work, etc) - I'd have to charge either more than once per day, or at whatever random point throughout the day the battery gets low.

With that in mind, I started looking at some of the other smart watches on the market. The Pixel watch isn't much more impressive at a claimed 24 hours, and the Galaxy Watch is a bit better with a claimed 40 hours.

Then I turned to fitness trackers. Fitbit has the Versa and the Sense which each have a 1.58" 268 PPI AMOLED display and a pretty similar array of sensors to the Apple Watch (The Versa has a few less), and both with a claimed 6 day battery life. Garmin has the Venu with a 1.41" 341 PPI AMOLED display, also with similar sensors and a claimed 11 day battery life. All have the same communication options (Bluetooth, GPS, NFC, Wi-Fi, I'm not interested in cellular). Even with the assumption that Fitbit and Garmin are exaggerating their battery life and Apple isn't, that's close to 10x the battery life. Even if they're exaggerating their battery life by double, they still smoke the Apple Watch.

Can somebody explain what I'm missing? I'd expect the display to make up a big part of power consumption, but they're all pretty similar. GPS seems like it could be a power hog, but they all have it. The physical size is pretty similar so Apple doesn't seem to be using a way lower capacity battery. The Apple watch obviously has way more to offer in terms of apps and other non-fitness features, but if I'm not using those regularly will I see a substantially better battery life?