I mean, if you had a fusion generator that magically created one star's worth of energy on your desk you couldn't use it like that, since all the energy it made would eventually have to turn to heat (like, you might make pure electricity and not put out any heat, but if you used that electricity it would net out to the exact same temperature as the star would have been) . spreading out in a big circle around a star is the only way that makes sense to use that electricity.