The popular 3 makes of drone are DJi - 3DR - Yuneec
These guys dominate the market and their drones are geo fenced, i.e if you try to enter restricted airspace the drone will not enter it.
Nah, they don't come close to dominating the market. Cheaper drones from companies like Hubsan, SYMA, UDI, etc., probably outsell the above by 20:1 if not more in terms of units sold, and most of them are not geo-fenced (or even have GPS!)
Besides it's trivial to bypass geofencing. Plus more and more kids these days are making their own custom drones for cheap. Virtually none of the popular flight controllers enforce geo-fencing. KK, Pixhawk, Multiwii, etc.