No one had ever explained that to me! 😱😱

Often, only one half of that outlet is switched, while the other half stays permanently powered for clocks, chargers, or routers.
But there is no national electrical code that requires upside-down outlets for switched receptacles, and orientation alone never guarantees anything.
A flipped outlet might be switched, might be a safety preference, or might just reflect a previous owner’s taste.

The only reliable way to know is to test it with a lamp and the nearby switches.
Once you identify which outlets are switch-controlled, you can use them intentionally—and stop mistaking a perfectly good, “dead” outlet for a broken one.