They did, if the OEMs would contribute to the SuperCharging network.Honestly, what took them so long: Opening the North American Charging Standard
Edit: This would have made more sense to do five years ago ... why now?
Things since then:
The government funding requires charge stations can't be locked to a single OEM.
Startups have been pinging Tesla to use the connector.
Network has more capacity
Other cars have decent charge speeds
Relatedly, Tesla now has a process for re-enabling SuperCharging on salvage vehicles (news report).