On RCCL [does not apply to any other line] if you put your tips on your sea pass account, the voucher and envelope is a waste of paper. It is only done for the passengers peace of mind or ego. If your tips are on your account, your wait team and room steward WILL GET THE MONEY. Voucher or no voucher.
Think about it! An EASILY reproduced voucher can be turned in for CASH. Not hardly!