I had to go and read the docs to confirm this was true, I'm really surprised this has been removed (since Raspian Bookworm apparently). It was a ridiculously common way to configure wifi on RPis over the last decade!
It's the little paper cuts like this that really hurt on a platform who's original aims were to target the education market, there is still a mountain of tutorials online advising to drop in that file for wifi setup.
> a mountain of tutorials online advising to drop in that file for wifi
Cannot emphasize this enough. People with barely enough knowledge (“script kiddies” so to speak) are configuring and using RPi’s. They just want to follow the tutorial and get it working so they can do what they really want. (Eg image processing or run their 3D printer.) Nothing against this kind of user. I help them when, but…
This creates a situation where “the wrong tutorial” problem is unnecessarily easy to stumble on.
Networking on Linux in general seems to be very susceptible to "wrong tutorial" in recent years, what with distros switching between different network control suites.
So far, I've been a big fan of netplan (which I guess is tied in with cloud-init?). Dropping a YAML file that declares the network setup I want and lets a swappable renderer make it so on the backend is a nice change from the brittle-over-time series of commands that it took previously.