Signal integrity and ease of assembly. There's a lot of very high-speed connections really close together, which means they are going to interfere with each other. The "paddle card" allows you to maintain signal quality while you are spacing them out a bit for the wire connection.
This isn't nearly as important with USB-2-only cables, which makes the direct soldering possible. It's going to require making a custom connector, so it's not really surprising a lot of manufacturers just reuse the high-speed ones and stick with a paddle card.
What is the PCB for if it's technically possible to omit it?