Theoretically you get hyperspecific representatives. Maybe a district in the west would want to vote differently than a district in the east. Theoretically your vote is still just as valuable and you're voting with your geographic peers.

In reality it just gets optimized for party votes and you end up with this

The sort of idea of it is/was to give farmers and people living in rural i.e. less population dense areas a “fair” amount of voting power compared to cities. The idea does make sense to some extent, as city dwellers often make up a majority of the population, and are unlikely to have the farmers best interests in mind, which could be problematic for everyone. But this already shaky line of reasoning has been abused pretty much since its inception by the party in power to swing the vote in their favor by redrawing lines

Because it makes sense to have local districts represented in the state legislature?

Other than being able to use it to cheat in other to hold on to power?