Important trivia (that may not be completely accurate), most interstate rest stops are prohibited by federal law from selling anything except soft drinks and snacks, thanks to lobbying from a restaurant association decades ago. The NJTP and a few other state systems (PA turnpike, WV Turnpike, etc.) predate the interstate system, and were allowed to keep their already open service plazas. As a result of that law, installing pay-to-charge charging stations at interstate rest stops is practically impossible, except at the areas already grandfathered.
Plus without a real food service, interstate rest areas are not the most appealing charge station locations. While some states may have worked out a way around the federal regs, I don't think in general there are many exceptions to this rule. Perhaps on the I-5 electric corridor?
If anyone is more familiar with the interstate vending rules and how to work around them, I'd appreciate a comment.