Because no clear frontrunner emerged, and the data shows that Mitt Romney at the very least is a very vulnerable winner.
Romney got traditional, upscale, suburban, moderately conservative Republican voters. He did not do particularly well with Tea Party voters, and he did not do particularly well even with moderate Republicans, who went with Ron Paul.
Paul, by contrast, brought new voters into the process, and was able to win the independents who participated, as well as those who were looking for a true conservative. Rick Santorum did best with social conservatives, and won the Tea Party voters and very conservative constituencies.
This tells the White House that there are huge opportunities in this swing state. The President and his supporters understand that in a state Obama won by nine points in 2008, there will be a real opportunity to make inroads with independents, who until recently have overwhelmingly been trending away from the president.