I think for web or "backend for network" people, you are
always deploying into a hostile environment (the Internet) and so you really should be at least aware of basic security measures. If you consider yourself a professional in that field, it's table stakes.
If you're a game dev, you were taught to write optimized code that runs locally on a computer.
Not everything you do will run on the network, and networking/multiplayer might not be relevant every single time you ship a game. So it's less relevant (if still important)
