Once again, it may simply be a regional difference. We get loaners here, if they're available, whenever we bring the car in for repair. Paid or warranty. If it's a long repair and they don't have a loaner when you first drop it off, they let you know when they do have one available.
Yes, I have a 2014 model s, and it charges slowly! So I understand that issue.
As to the legality of it, that is a good question. I've never checked it out myself.
Interesting discussion!