Having worked in exactly the same domain , I can very well say that OTA is risky, moreover the data providers for the car is not really happy about OTA ( Sprint , AT& T provides connectivity for the projects I worked on.). They lease out a certain bandwidth to the connected cars which sends small bursts of data at a low contracted price. If the car manufacturers need OTA, they will have to pay a premium which will be slapped on the customer. There is also a technicality of downloading a huge image ( possibly 1 GB ) over a spotty network. ( a running car will switch cell networks , network types 3G , LTE , 1x , lost connections etc ).
Why only Tesla has OTA? Some people really think nobody in the industry ever thought of that since the internet was born? Musk is doing a nice publicity stunt.
Tesla sold, what?.... 30000 cars all time? All models above $50000? So addressing people living in places where OTA is not an issue.
How are all the other car makers going to handle a production of a few milion units PER YEAR, being updated OTA? How are they going to update cars sold in countries where Internet is a dream?
If you change your release strategy to fit an OTA update model, you better be able to support it. This is not a problem for the volume Tesla is selling, and neither for it's audience.