[Alneyan]

Imperial ego! Don't you want your own Sphereworld in your homesystem?

Ringworlds are a more realistic option, since they only require Stellar Manipulation V (against VIII for Sphereworlds), and they are cheaper to build. Their main use is to counter Star Destroyers, when these eventually become available. You cannot destroy a Ringworld, and saving your systems by building Ringworlds on important stars can be considered.