Legislators actually care a lot about the process of redistricting considering the fact that gerrymandering is a common practice in many US States. For example, a Democratic legislator might distribute their district to heavily favor democratic citizens that live in specific districts to ensure they would win the most districts upon reelection.
Another example could be a Republican legislator that draws a liberal city as one district and then distributes the rest of the districts to favor Republican parties.
These situations ultimately affect the election because of the idea of electoral-college style voting in which 60% of a blue district becomes the same number of votes as a 100% blue district.
