I say this having never driven a Tesla, but are they really suitable rental cars? My understanding is that Tesla vehicles differ quite a bit from regular ICE vehicles, to the point that there's a bit of a learning curve to operating the car. I'd be interested to hear from a Tesla owner on this. Maybe it's a non-issue.
I hopped in my Tesla for the first time and after a single stop sign where I stopped kind of weird (not honestly that bad), that was it. The Tesla person on the initial lesson assumed I'd driven one before. You get the hang of it really quick. Same story for many other people who've driven my car. If you're not using regenerative breaking it's pretty much like a normal car sans the small acceleration gas cars provide…
Gas automatic cars :)