Are you talking about "systems that cannot be reached in just one jump" ?
Follow up to that is: don't most systems have at-least one space station where you can stop-in and buy fuel?
Just takes multiple fuel stops, then, to get farther?
You're correct. Most multi-jumps don't even seem to require refuelling - you can jump at least three times on a tank of fuel in a Sidewinder. Max range is determined by your hyperdrive and the ship mass.