Social Identity Theory could be very useful here. It basically says that we join groups where membership will raise our self-esteem and we quit groups where membership lowers our self-esteem.

Here are some of the top articles on the subject:

https://scholar.google.com/scholar?q=social+identity+and+organizations

In examining why employees decide to join unions Schuler and Youngblood (1986) have developed a model. According to them, there are three separate conditions that strongly influence an employee’s decision to join a union i.e., dissatisfaction, lack of power, and union instrumentality.

Schuler and Youngblood (1986, p. 550) note:

“When an individual takes a job, certain conditions of employment (wages, hours, and type of work) are specified in the employment contract. A psychological contract also exists between employer and employee, consisting of the unspecified expectations of the employee about reasonable working conditions, requirements of the work itself, the level of effort that should be expended on the job, and the nature of the authority the employer should have in directing the employee’s work. These expectations are related to the employee’s desire to satisfy certain personal preferences in the work place. The degree to which the organization fulfils these preferences determines the employee’s level of satisfaction”.

Schuler, R.S. and Youngblood, B.S.A. (1986), Effective Personnel Management, 2nd ed., New York: West Publishing Company.

Yes many thanks for the inputs. The S&Y (1986) focuses on the three factor and SIT is truly a worth theory to explore