Well, they did make sense back until (and including) the industrial age, when it made economic sense to invade territory, and either start using local factories

Well, they did make sense back until (and including) the industrial age, when it made economic sense to invade territory, and either start using local factories or just loot machinery and bring it back to the home country. But that time is gone, there is nothing you could loot right now that could justify the cost of an invasion.