ACTIVITY_ID and BUSINESS_UNIT_PC chartfilelds are activated automatically by configuration process

While activating CHARTFIELD1, configuration process is also activating ACTIVITY_ID and BUSINESS_UNIT_PC even though they are not selected on Standard configuration page. We don't use Project costing but have expenses module. However, we don't want to setup ACTIVITY_ID and BUSINESS_UNIT_PC chartfields. Please advise how can we avoid these two chartfields being activated by configuration process.