What is the purpose of having more than 1 PCIe x16 slots?

Computer Does Not Boot With PCIe Card in x16 Slot - NI pcie x 16 slot pciex16 #GPUinstall #howtoinstallgpu #GPU #graphicscard installing any pc component is pcie x4 in x16 slot PCIe boards can fit into slots designed for their lane configuration or higher Plugging a x4 PCIe into a x16 slot is acceptable

pcie 30 x4 slot List of Motherboards with 1 PCI-Express x16 Slots: ASRock B760M-H, ASRock H610MAC, ASRock B760M-HDV, ASRock H610M-HDV+ D5, GIGABYTE B650M D3HP,