There is at least one residential building in Vancouver, BC that has implemented an automated system, but according to this article, the cost per space is almost double that of a conventional space:

http://www.vancourier.com/news/vancouver-robo-garage-lowers-...

Also, having spoken to someone who lives in that building, it seems to be disliked by a lot of residents, due to the long waiting times at peak periods. That's not particularly surprising given there are only two transfer stations.

I guess these systems may work better in retail locations where there is a steady flow of traffic coming and going through the day, rather than at residential or office locations where there are very high peaks in demand. To build enough transfer stations to satisfy the peaks would presumably both be very expensive, and reduce the space savings that were made.

Cost and retrofit requirements, mostly.