The only reason to cross county lines is when counties lack sufficient population to form a district on their own. In counties with a population for more than one district, it should be split with the straightest of lines. For example, look at where Texas wants to violate this logic here. Why? The GOP is unhappy with having 66% of Texas districts and wants at least 80%. The lines get so squirrely because, according to 2020 data, approximately 84% of Texans live in urban areas. People in urban areas tend to lean left because they are exposed to diverse groups of people more frequently. So you see GOP-drawn maps taking several low-population counties into a district with a sliver of a populous county to dilute the urban vote. Zoom into any county with a population large enough to be its own district, and you will see how it’s been divided to suppress the voice of that 84%.