Some people can. Many can't.
California recognizes no other states' permits. Oregon recognizes no other states' permits but will issue to residents of neighboring states on a "may-issue" basis. That leaves only Washington as a route to the Pacific. Washington recognizes Nevada but not the easier to obtain Utah or Florida permits (at least as I recall).
So, if you are a Washington resident with a Washington permit you can travel that route from, let's say, Georgia to Washington.
South Carolina and, more recently Pennsylvania, refuse to recognize permits held by non-residents of the state issuing the permit. South Carolina doesn't recognize my California permit and has never recognized any of my other permits because I am not a resident of those states. I can't understand why Pennsylvania has drifted to the dark side.
Many counties in Pennsylvania, but not all, will issue to non-residents. The problem is that you have to appear in person to be issued the permit. I may be visiting a relative in Pennsylvania soon and may just check out the process.
South Carolina doesn’t recognize my California permit
Since California doens’t recognize anyone’s, that I know, there’s no reason for SC to recognize Cali’s. Quid pro Quo, in its most basic form.
It all comes down to the state legislatures. They meet, they talk, they agree or disagree. Simple as that.