They don’t even need the tunnels right now—they have plenty of humans to act as mules.Most drones only have a payload capacity of a few ounces. Let’s say you can somehow cram 8oz of fentanyl onto a drone, you still only have an operating range of 1-2 miles, and have to deal with being seen, seeing, weather, and finding your destination.
Or, you can use a tunnel (there’s a ton of those) and be able to get 40-50lb of that crap across per person, without having to worry about technical issues, the border patrol seeing your aircraft, getting lost, etc etc.
I would be picking the tunnels. The cartel typically does too. Although there have been accounts of drones, trebuchets, aircraft, submarines, etc being used to transport drugs. Why invent a new, less efficient, much more expensive wheel when you already have one or two wheels that still work?