For those who do not believe that self driving is not a big deal, just imagine if Tesla made an announcement that it was going to be turned off for a while for all those used to using it. Riots in the streets.
That does raise a good point about why it's probably so easy for them to "add" it over the air, but may not be so easy (or wise) to remove it over the air. I can't think of the software even having the need for a "remove autopilot" use case... So it may not even have been built.