Good Reason For Changing Job From Private To Govt

Hi,
I have around 5 year of work experience in a private company. And now I am trying for Govt job. In one interview, interviewee asked me reason for this big change.
I gave them following reasons:
a. Job Security
b. Money is not matter for me
But they're not satisfied with the answer.
What will be best answer for me? Help me in getting the answer.
Thanks in advance.

Dear pranjuls
Welcome to CiteHR.com.
In an interview, some subjective questions are asked to elicit an opinion and to gauge the attitude and beliefs of the person.
Since such questions do not have a definite, precise answers; the best answers are those which you consider to be true.
However, at times, the interviewer may be looking for an "ideal" answer rather than a "true" answer. For example, in this case, they might be looking for an answer that reflects a sense of "patriotism", like :
"I have always wanted to serve the country in a meaningful way and a government job will provide me that opportunity and a sense of pride."
Warm regards.

Thanks for reply.... I'll start preparing myself by keeping your point in mind...
One More doubt is here.....
What should be reply when interviewer will ask me to tell something about me? What points should be included? Should I quote the reason for changing from Private to Govt?

Dear pranjuls
When you are asked, "..tell me something about yourself.." your response should not include the reasons for change. Just tell them about yourself, starting briefly with your background and more specifically about your qualifications and experience.
This question, although meant as an 'ice-breaker' to start the interview, sets the tone. The data about the person is already with the interviewers, but a good interviewer observes how the interviewee sees himself, describes, presents and expresses himself. A skillful interviewee can put this question to his advantage by expressing his unique qualities, values and attitudes in an appropriate manner.
While preparing, do not mug up your answers and rattle them in the interview. Nothing irritates an interviewer more than 'ready made stock' answers lacking originality and truth.