to be more specific read this. and you shall find the truth finally......
There are several reasons why a company would choose to operate a wholly owned subsidiary, rather than simply absorb the acquired company into the central corporate operation. One of the most common reasons is a matter of location. The wholly-owned subsidiary may physically reside in a different country from the holding company. When this is the case, there may be compelling financial and regulatory factors that make it much more financially sound to allow the company to continue more or less autonomously.
Another common reason for the operating the wholly-owned subsidiary separately from the owner company could be name value. Often, a well-known and respected corporation is acquired by another entity that has no name recognition in that particular market. Rather than spend huge amounts of time and resources to create a reputation, the holding company will simply decide to remain in the background. This allows the wholly-owned subsidiary to continue to enjoy the current name recognition and market share, while being able to work with the resources of the parent company to find ways to enhance that reputation.