Why does VS not define the alternative tokens for logical operators?

You ask about the rationale. Here's one possible reason, not necessarily the one that most influenced the Visual C++ team:

1. Those are valid identifiers in C.
2. Microsoft's recommendation has long been to use C++ mode for both C and C++ code, rather than maintaining a modern C compiler.
3. Valid C code using these as identifiers would gratuitously break if they were compiled as keywords.
4. People trying to write portable C++ are mostly using /permissive- or /Za for maximum conformance anyway, which will cause these to be treated as keywords.
5. The workaround to treat them as keywords in /Ze by including a header file is easy and portable. (G++'s workaround -fno-operator-names isn't bad either, but putting the option in the source code rather than the build system is somewhat nicer.)

VS is nonconforming. This is old news.

To use alternative tokens, include the <ciso646> header. According to the standard, including this header is supposed to have no effect in C++. However, you do need it in VS. So it's safe to just include it always, whenever there is any chance that you might be compiling with VS.