Because it's easier on the non-Pacific time folks. Instead of Eastern time folks starting at 1300, they start at 1100. It also helps coworkers who want to move to other parts of the US, at the expense of those of us still in Pacific timezones. This way Eastern time folks can sign off at 1900 instead of 2100, which makes it easier for us to work synchronously if needed across the US. Before we went all remote we tended to hire in the same time zone but now we hire across the US. Pacific time workers have to take the early bird hit. If we operated the same as before then we'd have extra morning time, but going remote means we now hire many more coworker in other timezones. It's a double edged sword.

We do also tend to end earlier. I don't care because I'm a night owl, but early bird coworkers seem to enjoy the extra time. And yes I've considered walking but haven't yet because I'm not so sure it's that different in other companies I'm interested in at my level.