When I was single and had fewer clothes I only separated when washing new clothes to avoid bleeding colors. After being washed once I didn’t care and never ran into issues.

Now they are separated because it makes sorting easier as most socks are in the light/white load and don’t get spread out across multiple loads. Reduces mismatches.

Towels are separate for the same reason, just easier to manage a bunch of towels than mixed clothes and towels.