Or can afford that kind of thing, and just want to impress their friends I suppose.
I see no other real reason for it car wise, I might have other applications of course, like in air refueling on an aircraft I guess.
The point is self-charging. Their Autopilot feature can drive the car to your front door based on your schedule, so if you leave the house every day at 6am, the car will be waiting for you fully charged, air-conditioned (or heated in the winter), with your favorite music playing, ready to drive you to work. The self-charging system lets it drop you off at home, open the garage door itself, drive & park, have the arm swing out to charge itself up, and shut the garage door. It's basically like a taxi service (well, once they get it the self-charging system on the market).
There's a Bosch system available for the Leaf that actually does wireless charging (slower to charge, but all you have to do is drive over a frisbee-shaped puck on your garage floor). The catch is that the Leaf only goes 80 miles & the Tesla goes 300, so they haven't figured out a way of doing wireless charging yet, at least not without giving you cancer in the process, or melting your legs off as you walk by due to the power transfer. This would be cool too for future parking lots...the overhang has a solar panel array & it can trick-charge your car wirelessly in the spot. Edit: there's a new model, looks like it supports the Prius & stuff now too:
https://www.pluglesspower.com/