It's important to look at this in the context of overall auto theft trends. Auto theft has dropped by more than 50% over the past decade, driven mostly by the broad use of smart keys. (http://www.iii.org/issue-update/auto-theft). The lion's share of the thefts are of older cars (mentioned in the above cite) -- thefts of 2013 vehicles number in the hundreds.
Further, a Tesla has a GPS, sophisticated processor, and a 4G WAN. It would be easy enough to have the car report back to the owner if it's being driven without sensing the key, and give the owner the option to route a theft report and live location of the vehicle to police with one click. That's something I wished for in my revenge fantasies when my car was stolen a decade ago.
We could do more, sure -- but it's hard to argue that we are making cars less secure, or even that car security should be a major care-about for the buyer.
Your opinion is an unpopular one, albeit one I share.
There are far too many cases where security is getting removed in the name of convenience, and this is no exception.