The Wordsmith's Forge

>> Drones aren't that cheap, yet. <<

Nor that easy. They can't be hidden near as well and are easily shot down. They can be hacked, too, whereas dumb mines cannot.

>> But if you factor in the cost of removal then they work out cheaper. <<

You have to hang onto your territory long enough for that to matter.

>>I think the problem is that military strategists tends towards being conservative.<<

That's one reason, but mines have a lot of other advantages.