So basically its a way of avoiding taxes then right? Thnx~ :)
It can be. If Mike preferred that the person who takes under the will receive the funds instead of himself, and let's say Mike would have given that person the money anyway, then by disclaiming he avoided making a potentially taxable gift.
Another thing Mike could have been doing is letting the funds go to a trust for his benefit if one was set up in your father's will. Depending on the trust terms, Mike could want the creditor protection of the trust (sometimes called a spendthrift trust).
There are several good reasons a person may decide to file a disclaimer. Another tool in the estate planner's toolbox!