Here is the easy example:

A dual 100GbE NIC requires a PCIe Gen4 x16 slot to run both ports at full speed. Mellanox ConnectX-6 200GbE cards require either 2x Gen4 or 1x Gen5 slot for full dual port bandwidth. Most of the larger NVMEoF nodes we are seeing are using more than one 100GbE NIC.

Enterprise SSDs will rapidly fill Gen4 x4 lanes later this year as we start to see them launch alongside more mainstream platforms. Four of those will fill a x16 slot.

GPUs and PCIe switches are also great examples of uses.

You are right that for the high-volume server segment, 160 PCIe lanes are overkill, as is even 128 today frankly. For some context, there is a huge portion of servers sold with less than 1 DIMM per RAM channel installed.