Why DHCP Server is required

why we use DHCP server(2012, 2016, 2019), when i have already created ip dhcp pool on router.
Yesterday i was done lab also, dhcp worked properly.

(But today I just checked on our L3 device sh ip dhcp pool … there are no dhcp pool created.

then how to work dhcp here?

PFA-created scope like this…

If you created DHCP pool on router the command will display on Router only not on other devices.

These DHCP pools are created in windows Server and they are just names of departments.

There are no other devices(like router), we are using only L3 device…and checked on L3 device , no pools are created here.

Than You have a separate DHCP server. You can configure DHCP in windows Server, Linux machines also.