Why do managers resist delegating work to their employees or empowering their workes?

This is not a generic situation. it varies person to person. Some Managers (Leaders) are happy to delegate their work and empower people and some are not. There can be many reasons which depend on an individuals skills, mindset and managerial style. some of the generic reasons may be as under.

1. Dictorial managerial style.

2. Conserve mentality.

3. Threat of subordinates becoming better than him.

4. Wants to retain power

1. Lack of trust to subordinate or supervisee.

2. Lack of knowledge, skills and experience.

3. Lack of confidence his or her responsibility.

4. Feel threats by the supervisee.

I agree with the answer of Saiful Islam Hiron.

This may be due to matter of satisfaction and achieve the goal on time.

manager/ leader is made so that he is taking out work from its sub ordinates to achive goals. However its a managers responibility to delegate jobs. A manager should not delegate a job when he doesnt believe in a subordinate can achive the goal or he doesnt have the capability to do so

If you are capable and your manager is not delegating, try to convince your manager with your skills that he belives in you and delegates the job to you.

However there is one problem these days, if you are capable and manager is not delegating job and excusing. They are scared of their own jobs, what if you can do the job the same way or do better then him/her he might be fired. I know lot of managers reading this might not like the statement but they will internally somewhere will know that this is true. 

MISTRUST and fear of loosing position,,, 

Generally this do not happen, perhaps the situation is reverse.

But if employee is not capable than its a different thing.

Interesting question.

There can be many reasons why some managers do not delegate; lack of skill or experience in managing people, trust in their team/employees, unwillingness to let go of functions which they previously owned or excelled at, fear of the challenge or being overshadowed, fear of inability to deliver (hence micro-managing), fear for their own role or job security, their own personal psychological makeup or ultimately, a combination of any of these factors +/- others

Ultimately, management is more about people rather than functional execution of tasks and that is what first needs to be acknowledged. There is also a BIG difference between management and leadership which is where managers are ultimately moving towards. Some are born innately knowing how to lead, others pick it up and wear it well, some may grow into it with experience and training but it's more about the change in mindset that goes with it from being a worker to a manager to a leader.

To quote an excerpt from a treatment by Alan Murray on behalf of the WSJ, where a non-manager focuses on execution:

The manager focuses on systems and structure; the leader focuses on people.

The manager relies on control; the leader inspires trust.

The manager does things right; the leader does the right thing.

The manager maintains; the leader develops.

Effective management comes from managers understanding their responsibilities and what is being asked of them and most importantly, knowing their team and what each in the team can do. Knowing the team will help build trust which should lead to empowerment. Managers need to recognise their teams skills and where there may be gaps that need to be filled rather than filling it themselves, be they training for employees or adding resources where possible so everyone has a sense of progression.

With that done and the team more self-sustaining, the manager should be able to free up more time to then be able to take up more/new responsibilities themselves which can enable their own progression and that of their team.

It is understandable from newly appointed managers hwo are just starting the career. They are trying to prove them selves. Any other case indicate a weakness and the reasons could be job security or lack of skills. Another reason might be the preference of their superiors.