Like when you send a .7z instead of a .zip or .rar to a friend or a teacher because that’s what your computer has installed and they’re like “Oh No, not one of those, now I have to install 7Zip” even though the same program that opens .rar also opens .7z I feel like people are way more annoyed when they receive a .7z
Normally it means that people have to set their network IP when they connect their device since they are not automatically assigned one. If the IP is taken, the router will tell you. If you don’t set an IP, the connection will simply fail. You are basically forcing every device in your network to have a static IP.
The upside is that you don’t have changing IPs in your network. I use my phone to control Kodi on my RPi and if I didn’t force a static IP on it, I would have to search for the Kodi host probably every time I restart the RPi.
Most routers and host clients do support IP reservation while still having DHCP enabled tho, so disabling DHCP is not really necessary these days. It wasn’t so smooth 20 years ago tho.