Because people in the same timezone are mostly at lunch and starting to relax for the weekend, so the potential audience is large. I wasn't thinking of anything market-related as another person suggested.
You're probably right. After-hours trading is so large these days that the big movers don't care when the news is announced.
Markets close at 1pm PT/4pm ET though I wouldn’t think investors would care (and judging by lack of movement it seems to be the case)
1pm PT is 4pm ET, and as we know from cron, 4pm is teatime.