The preprocessor is stupid. It is just a glorified automatic search/replace engine.

The compiler, on the other hand, knows about data types.

So a good compiler can generate warnings if you have a switch statement that misses handling of one or more enum values - it would not know anything if you used #define.

Since enum represents data types, you can specify these data types when you create variables or member fields of structures. If you program with #define, you must settle for char, int, ... as data type. But a field of type "unsigned char" does not tell the reader that the field is expected to only contain valid action types. A field of type "Action" will tell the developer what is expected. And will allow the compiler to generate a warning if you try to assign a value not part of the "Action" enumeration.