1, funding constraints: the unit budget has certain constraints, which cannot cover all employees' paper typesetting expenses. In this case, the Unit will choose to reimburse only certain types or highly important documents.
2. Differences in publishing requirements of papers: Different fields and disciplines have different publishing requirements for journals. Journals are regarded as core journals or have high influence, and publishing articles in this journal often requires high page fees. Due to the differences in the definitions of core journals and non-core journals in different disciplines and research directions, some units choose to reimburse only the editions published within a specific level or scope.