Most—maybe damn near all—sites see significant dips in traffic for at least a few hours a day. Which part of the day, depends on the site. More often than not, it's while the team is asleep and staffing, if any, is at its lowest point, since teams tend to live roughly in the same ~half of the world that their products are most-used in. Plus there's practically no-one in the Pacific until you reach Japan, and not a ton of "Western" sites see much use in Asia, and vice versa, with a few notable exceptions.

It's not unusual for e.g. ecommerce sites to crank up automated fraud prevention "at night" because staffing is so much lower.

TL;DR Most sites' usage patterns exhibit a pronounced day/night cycle that's not too far off from natural day/night cycles where the bulk of the team lives.

Not uncommon before the intro of edge services to block login on sites during off working hours or during nights. Or at least doing some rate-limiting. We see many attempts at brute force-attacks during the nights. Most sites are not global.