[Fyron]

Drones are good against AI because the AI is stupid and can be defeated by nearly anything, used properly. But against other humans in a pitched war, drones are only useful (as a primary tactic) if you had a long period of peace in which to build up large stockpiles. Otherwise, it is too costly to amass the number of drones quickly that you need to be able to take out a good sized fleet. And even if you manage it, the drones are all used up, leaving you open to the next big fleet, which with most players is not going to be far behind.