Why would a PCIe x16 slot be limited to PCIe x1 card?

Why would a PCIe x16 slot be limited to PCIe x1 card? pcie x1 slot function PCIE SLOTS AND CARDS A PCIe or PCI express slot is the point of connection between your PC's “peripheral components” and the motherboard The pcie slot cover Providing total bandwidth up to 250MBps from the PCIe x1 host controller card allows the computer to function as though the expansion chassis cards were

pcie slot cover 2*PCIe x1 5 EZ-Latch 6 Socket AM5 Supports AMD Ryzen Unlock the latch of the PCIe slot easily when remove the graphics card in the PCIe slot

pciex16 slot configuration PCIe Gen 2 x4 or x1 root ports; CoprocessorAccelerator slot, a USB debug interface, and a mikroBus connector for expansion  PCIe interface, slot and mounting multiple cards in one computer Computer motherboard may have PCIe slots compatible with x1, x4, x8 and x16 When users need