What are the top uses of PCIe x1 Slots?

What is the point of even buying a video card that uses PCIe if people have motherboards that only have PCIe slots?

PCIe doubles the throughput rate per lane, giving users a transfer rate of up to 64GBs Why does this matter? The faster the throughput

30 slot mailbox PCIe boards can fit into slots designed for their lane configuration or higher Plugging a x4 PCIe into a x16 slot is acceptable

action slot 4-3, per single PCI Segment Group show less , ECN, November 18 with the link layer requirements in Chapter 3 of the PCI Express Base Specification