Myth: A sock can't do much about what your feet go through.
Fact: It literally sits right between the skin and the shoe. If anything, it's one of the only things that can. The right sock reduces friction and moves sweat before either becomes a problem.
Think about the geometry. The sock is the single layer in direct contact with your skin on one side and your shoe on the other. That's not a minor role — it's the interface where friction and moisture are decided.
Research backs the leverage point: socks with low friction against the foot's skin reduced plantar shear more than socks designed to slide against the insole. Move the sweat, cut the shear, and you've addressed both blister triggers at the exact layer they occur. That's the Foot–Sock–Shoe System doing its job.
Source: Sock friction & plantar shear (Medscape, Friction Blisters overview).