I too am a employer ... And yes, i expect people to prove their worth. I also believe in paying them for the value they initially bring to the table .... It's a simple measure of respect.
Unpaid internships and apprenticeships have a place in the educational world ... And often students receive college credit for them, which is a form of payment.
The real world answer is that we cannot legally bind anyone to employment ... Slavery was abolished a long time ago. People stay in jobs where they are treated with respect and valued. Employers keep people who perform and care.
Good work relationships are mutual .... Always have been always will be.....