WAN will create a new network with a different IP address. And only routers are made with this function.
Using routers are convenient for communities like companies, restaurants, buildings.
We can see most of these organization made with multiple departments, floors, branches, therefore, having different LAN will be easier to manage. Besides, having various networks for particular groups can remain a good connection in a large area.
LAN can distribute internet to other computers, but it cannot create another network.
This network connects computers and retains them in a confidential link. Devices using the same IP address can share data because they use the same IP address.
It keeps everything under control, but LAN is only active for a certain number of users. So, we usually recommend this type of system for a small scaled organization like houses or café.