Every program in RSLogix 5000 has its own program tags. All tags created in Program tags have a scope within the program itself. These tags are seen as local tags. Two programs cannot share the same tag. If for any reason you want to share tags between programs then those tags should be created in the Controller tags section.
Since no tags could be shared between programs then the same tag could be created in more than one program. This means that programs could be copied and reused more easily since we don't need to worry about tag conflicts between programs.