Why did workers want to engage in collective bargaining when negotiating with an employer

I believe it is workers had more negotiating power when standing together as a group rather than they had individually," since it would be very detrimental to a company if their entire workforce quit at once.

If the worker wanted to easily get the job, they would negotiate a bargain with the employer, which is extremely unethical in the business world today. If the employer took the offer if would be wrong and be kept secret among both the employer and the newly hired employee.