The advantage of a fast WAN is you can put it into a capable router (2.5-5-10g) and break it out into multiple clients who can use it simultaneously even if at only 1g each.

This also applies for wireless technology. My phone generally gets a faster connection via 4G, than via WiFi inside my house (the cable connection is fast, but the WiFi is slow). I think because the 4G connection can always see a tower through a window opening, while the WiFi has to go through multiple walls. (No interest in setting up a mesh network as the 4G is plenty fast enough)