Personally I've been using Ultimate on and off over the years, since I've never really stuck to any one language; at my previous job it was a mix of PHP / JS (Dojo), Go, Typescript, and sometimes (reading) C code which didn't quite work right in Ultimate.
VS Code can do all that too, but only intellij was able to actually help me with stuff - things like set the version of PHP to 5.2 so it warns me if I tried to use the PHP 5.3 array shorthand. (I did not choose PHP by the way and the project was to replace it)
They're for different audiences; the hurdle of trying to explain to a JS dev "yeah, I know when it starts up it asks for a Maven/Gradle/JVM, but just ignore that and open a directory after you install the following 8 plugins" is bad DX. As others have said, the standalone products are not feature parity with the IJ plugins. I have no idea why that is, or what incentives are driving that, but for the time being it is what it is
Probably to sell their more expensive "all access pass" instead of just one IDE that does everything.
VS Code is getting support for all the newer languages though... similar to how it used to be before with Eclipse (for those who remember the multitude of Eclipse-based IDEs for niche uses in the 2000's) and emacs (which still gets support for most esoteric langs, even if half baked, pretty quickly)... for example, I can use Zig in both emacs and VS Code, but not IntelliJ (I think they are writing one , but it was really unusable when I last checked it out). And stuff like Julia, Common Lisp.... I tend to go to emacs for those... but apparently supporting VS Code is high priority for even these languages nowadays.
Android Studio's C++ support is done by Google's own licensed CLion for integrating it into a proper development experience.