

For the same reason that countries exist. Everyone should have the right for representation. The US is a big place. It needs to be broken into individual locations so that citizens are better locally represented. Whether or not the seemingly arbitrary lines make sense is a different debate, but have some level of boundaries should exist due to the size of this country.
You haven’t provided any counter. I’ve told you why they should exist. You’ve said they shouldn’t with no reason. What is your better solution that will be better and why?