Do you think that's because it's far easier to charge your car at home while you are sleeping? And that renters who lack this convenience or face difficulty achieving it might be put out by the experience during a possibly expensive and rare vacation?
I've tried 3rd party chargers a few times and gave up on them. They're often broken or extremely slow. They usually require installing some app, and you don't know whether they're occupied or not until you get there. In contrast, Tesla's chargers are a consistently good experience. Without them, I'd simply never use my EV for road trips.
I still use other charging networks from time to time. The best that I can say is that they are usable, but they are often frustrating in various weird ways.
But that's not why I mentioned Tesla. I mentioned them because there's so much weird industry caused complexity that they avoid. Need to charge the car you've just rented? Just find a supercharger and plug in. Not ideal necessarily, but at least it isn't hard.
Got a non-Tesla and need to use EVGo or EA? If you're lucky the card reader isn't broken. Then there's a decent chance it times out while communicating, because the order of events isn't intuitive for first timers. Cancelling the session at this point sometimes gets tricky too. Oh, and all of this is assuming the unit itself wasn't broken. If the card reader was broken, now you are downloading an app, tapping in card details, trying to figure out which stall to active, etc. And finally, you find out that the Bolt might require you to hold the cord just right for it to activate. EA used to have a whole video just on this detail. :facepalm
It can be a really terrible experience.
TBH, the experience of most Tesla owners is just put the dest in the map and charge when needed on the way.
The one clear problem that is highlighted in that article is that hotel, or more generally destination, charging makes a huge difference. People think it is all about getting there, but it really is the being there that can be tricky.
Rental cars magnify this problem, which is why it was so strange that Hertz expanded the fleet so rapidly. Scaling the same move over 3 years would have had very different results(*).
(*) Maybe other than maintenance costs. There were odd rental effects in that from the stories that I've heard.