Why?
I run 11 security cameras at the house, in their setup I establish a static IP.
I also do this for other devices , the Roku units, the Ooma VoIP set up, the servers , like the NVR, The DNL, and the TVs
Anything I can Static from the device, I will
I'm using Asus routers (3) , 1 as primary and 2 as APs
I have roughly 60 things connected.
Now there is a benefit to not having certain items static at the device, that would be for items, laptops, cellphone , that will move outside your network... like taking your laptop to work, you don't want the adapter to be static, but only static at home, for that , yes static it at the router.
Benefit of Static, overall, at the device, your router goes south, dies, recovery is easier if the individual items are static IP