People aren't leaving. It's more due to deaths outpacing births. A lot of portions of PA got hit bad during the economic collapses of the 70s-80s, so there are a lot of places where you have a lot of elderly, some baby boomers, and young people leaving. Pittsburgh reversed the trend, but there is a noticeable absence of Gen X and younger boomers in the region, due to that generation getting pushed out due to the lack of jobs. Steelers nation became a nationwide thing because of how many people left when the steel industry collapsed. Covid nailed the elderly severely and they are just old and dieing naturally.