The reason for this is because of Islamic Sunni code. Because it is such a great offense to idol worship, Muhammad is not physically portrayed in painting or currency. The Sunni persecute the Shia over shrines to their "martyrs" because it offers an alternate source to worpship other than God. There are no "Marys" or "Saints" within Islam to commemorate events and invoke a measure of prayer and worship. Ali is as close a dead martyr you are going to get (within the Shia sect only). The Sunni hate the memory of Ali (90 percent of Islam report to be Sunni). The truth is for all of Islam's preaching about their dead, they move on quite quickly. He may become a martyr in local thought, but other than that he is forgotton. He is a gravestone. A shallow memory. Where are the attacks to avenge Osama Bin Laden's death? Even if a future terrorist attack develops, the event will simply use his death as an excuse (any excuse will do). An imprisoned Osama Bin Laden would give plenty of excuses to people who are always looking for one and they will always have their living "political prisoners."
Therefore, Osama Bin Laden is just another dead asshole in the long war against infidels and Western oppression. Tossing him in the ocean merely closed the book without the long drawn out media splashing that would have invoked angers.