One’s role or designation decides that he or she will continue or not. If someone is not getting the role as they want then that person might resign from the current position unless you are giving him a chance to grow.
That’s the most important reason that people left. There can be different scenarios:
If one is not getting the salary he deserve as per his experience.
If he is not getting the salary as he expected.
If a company considers previous salary for current salary increment.
If an employee has responsibilities which are too much or out of his area of interest then may person can switch. One other reason behind job change is that if a person has responsibilities of his interest and he has interests in some other areas as well and he wants to explore himself but not getting a chance.
Every company has their own work culture like how they work and all. It’s not necessary that every employee likes your work culture. People have their own mindsets, may be some can not fit in every culture or process of work or may be some has their own way of work. In this case companies can not do anything unless finding a person who has worked in a company like yours.
Colleagues behavior or team bonding
May be your employees are very fun loving and good with everyone but may be they are not ready for one new employee. Its human tendency that they make friends everywhere they go or live. One new employee can feel awkward with your old employees if they already have their groups and secrets. Yes, it also happens in offices.