The districts are set by the states, so I assume wherever you have a state legislature that heavily leans one way or the other they will meddle with the districts over time to help their own party.
I'm trying not to be rude but - Captain Obvious, that is EXACTLY what happens.
And people are trying to stop that, aside from the fact that it's simply ridiculous to have these tortuous shapes call a voting district.
But they get created for many reasons. For example, the rules and constraints of the Voting Rights Act are confusing as hell, but they DO state that race should play a factor in creating districts. I'm confused by them also, because obviously you can draw districts that overstack minorities into ONE district so as to minimize their effect - or you can spread them out over a few to maximize their effect (in the event the minority FAVORS your party).
Obviously, according to the Constitution, districts are *supposed* to be nearly the same in population - but what often means is - irrespective of race and party - that districts will include parts of a more populous area that may have completely different interests. A typical example is our own - it would be great if we had a "Southern Maryland" district where our rep would deal with issues unique to this area - but there ain't enough people. They HAVE to include voters from either PG or Annapolis. And honestly, once THAT happens, the voters in those regions have a bigger say in what happens with our rep in the House.
So a common consideration in trying to create fair but compact districts is to consider historical and regional interests - and that can be hard. You can bet that if you're a rural part of a district where most of the voters live near a city - your interests in creating some kind of interstate tunnel or bridge is likely to get ignored.
