A Supreme Court opinion has several functions: 1) it resolves a real live dispute between two parties; 2) it gives guidance to the other federal courts; 3) it serves as a statement of the law to the public.

For (1), you want to publish immediately, because the parties have already waited a long time to get the dispute resolved. For (2), you want to publish quickly, because the federal Courts of Appeal need to implement the new guidance in other cases, and may be holding cases that pose the same question pending the Supreme Court's resolution. For (3), you want to have enough time to polish something, because it will be referenced for decades to come.

The system of publishing a bench opinion, a slip opinion, and a final published opinion reflects these conflicting needs.

Approximately nobody in the US would rather wait for the final binding version of the opinion, for avoidance of uncertainty, than read about the bench opinion on CNN. The very few people who care about this issue already know they need to watch for the preliminary and bound opinions.

The SCOTUS website itself is excruciatingly clear about these points:

http://www.supremecourt.gov/opinions/info_opinions.aspx

Think of it as "open source justice", where more eyes means less bugs.