Approximately 45–50% of all pins in the AM4 pinout are VSS (ground) . Why so many? Ground pins provide a return path for current and reduce electrical noise between high-frequency signals. Every high-speed signal pair (PCIe, USB, DDR4) is surrounded by at least one ground pin. In the diagram, you will notice a "ground mesh" pattern—every third or fourth pin is VSS.
AM4 CPU provides 20 PCIe 3.0/4.0 lanes (Ryzen 3000/5000 = PCIe 4.0, older = 3.0): am4 pinout diagram
If you are probing your AM4 socket or CPU pins: Approximately 45–50% of all pins in the AM4