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

Why would a PCIe x16 slot be limited to PCIe x1 card? pcle x1 slot 1 additional PCI-Express x1 slot is needed pcle slot PCIe cards can always operate in PCIe slots with the same or more lanes than the card For example, an x8 card can operate in a slot with x8, x16, or x32 lanes

pcle slot Yes any pcie xanything card will work in a x16 slot, i have a pcie x1 asus xonar stx in a 16x slot right now x4 and x8 cards will also work in

pcle x1 slot Most of dual NICs need an x4 PCIe slot The end result would look like this picture : The only doubt SATA card for PCIe x1 slot with 8 ports Bizarro