Although it doesn't hurt to have cameras*.
And more to the original posting - they all know my password and I know theirs. If you can't trust your employees with that, you shouldn't be working with them. The cameras are mainly due to past vandalism and burglary.
*I purposely made it small & blurry to protect the innocents. Message me if you want to know how to build your own DIY, inexpensive cctv and wireless alarm system.