Why do organizations hesitate to admit and announce about occurrence of any fraud?

It creates a wrong impression about the company in the market. If they announce such things to the market there will be a question on the systems of the company and also there are chances they might get target to further frauds.

When we as human do mistake, we try to hide the same thinking what will people think about it. similarly it is with the company. Market place when it is more competitive everybody will try to find loop holes, this might be one of the reason for market to talk about your company.