Per diem rates cover tips for hotel maids (housekeeping)

The following describes US government per diem rates:

"Tips to porters, baggage carriers, bellhops, hotel maids, stewards or stewardesses and others on vessels, and hotel servants in foreign countries are included as part of incidental expenses covered by per diem. Tips related to meals are covered as part of your per diem meals expenses. Reimbursement of tips when authorized the use of taxicabs will be allowed, but is not included as an incidental expense."