Why is c++ redistibutable not included in Windows Update [closed]

Probably because:

• You can have multiple C++ redistributables installed.

• Some programs need specific versions. Like really big programs that companies use such as AutoCAD components, etc.

The C++ or any other language redistributable is more associated with a software developer's development environment (e.g. specific version of Visual Studio used to develop and build the executables) than the OS.

It's possible to use environments other than Visual Studio to develop Windows software so that's probably why it's not included--Microsoft is making that the developer's responsibility to get right (which they don't always do) rather than themselves.