system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] Why are large areas of the Galaxy still unexplored after thousands of years of interstellar travel?
gpt
Hyperspace is extremely hazardous when traveling an unmapped route, as any object of sufficient mass in real space creates dangerous hyperspace currents near their gravity well.  Without knowing where every object larger than, say, a large asteroid is, pilots run the risk of having their ship crushed by the forces of these currents.  While stars might be easily detected, other interstellar phenomena--rogue planets, for example--can kill an unprepared pilot before he has the chance to react.  It is worth noting that these currents can be compensated for in order to leave hyperspace close to a massive object, but not without detecting the object and calculating its effects on hyperspace first.

As for why the Unknown Regions remains largely unmapped, there has not been a major incentive to explore the galaxy further in nearly 10000 years.  Back then, when the major safe lanes of travel were being initially mapped, millions of explorers in thousands of ships were constantly making jumps into unknown territory, exposing themselves to severe risk in a chance to gain glory.  But the civilized galaxy has largely stagnated since then.  In addition, explorers who find themselves trying to map the Unknown Regions have a reputation for disappearing with a frequency that far exceeds what the already high rate of hyperspace accidents can account for, suggesting a more sinister presence outside the influence of civilization.