There are two parts to this: 1) Tesla needs to open up superchargers to other cars. They're doing this at scale now, but generally only the less popular ones,

There are two parts to this: 1) Tesla needs to open up superchargers to other cars. They're doing this at scale now, but generally only the less popular ones, or if they're required to do so by government grants. So many key sites are still off limits to others. 2) In the US only, other car manufacturers need to adopt Tesla's NACS charging standard, so they can physically connect to superchargers. (In the rest of world, everybody including Tesla is already standardized on CCS2.)