If you have had an opportunity to see the home you are about to buy, (believe it or not that is not always the case), you do not need a home inspector to point out the obvious. Knowing that home inspectors are performing a "Visual" inspection, why should you hire an inspector to simply report on the obvious?
1) Home inspectors are trained to understand what they are looking at. A lay person or even an experienced Real Estate agent may not always recognize a minor symptom being a signal of a major problem. For example an 1/8" horizontal crack in a foundation wall has great significance and may be the beginning of serious problems whereas a 1/8" vertical crack is generally the result of normal expansion and contraction. There are thousands of these types of examples.
2) As a home buyer, you are emotionally wrapped up in the transaction. Often times "Love is Blind". Yes this is true for real estate as well. You have decided to buy this house because it is your dream house. Wanting it so bad can cause you to overlook or minimized critical issues.