How exactly do they have an equitable relationship when their method of improving their own positions is essentially blackmail? If they had an equitable relationship with their employer they wouldn't need to strike every 6 months.
You do realise this is exactly the same inequitable relationship the employer has with the employee? Work unpaid overtime, or be fired. Work outside your job role, or be fired. Work without training, or be fired. Work for below minimum wage (and keep quiet about it), or be fired. Work under threat of being made redundant, or be fired.
The right of an employee to withdraw their labour is one of the few tools the employee has to assert themselves over the employer.