They are probably not very intuitive to use, but I find them a very fun part of the game. I tend to play with AI designs or designs not being way different than them, and managing fuel and range is one of the interesting things about the game.
Once I "start moving", I build a resupply ship or two, and park them on good fuel sources. If that doubles as a scanner position all the better. If I got a part of the empire with poor fuel supply, I may choose to deploy one there to fuel the defenders.
Whenever war happens, there will be some ship full of fuel that may move ahead and deploy, giving a very good fuel source. If the front moves, so will the resupply ship.
Some enjoy giant gas tanks and giant, fortified fuel mines. I enjoy managing fuel with resupply ships.