4. requires food, water, sleep 5. is a liability in dangerous jobs (large payout, bad publicity, etc if something goes wrong and is injuried) 6. needs vacatio

4. requires food, water, sleep 5. is a liability in dangerous jobs (large payout, bad publicity, etc if something goes wrong and is injuried) 6. needs vacation, weekends off, has friends and family, etc — can't go on a one-way trip into space for example.