-- The reason for WWE blaming Brock Lesnar and going with the current storyline of him balking at a challenger is once again an attempt to build up Roman Reigns as a babyface for when he faces Lesnar. This was the same plan for WrestleMania that proved to be an utter disaster as neither man was cheered and the crowd ended up hating the match. There is a very real danger of history repeating itself at SummerSlam, perhaps even worse, since it's an indoor crowd in New York.
-- The only change in the direction of the storyline is that this time WWE is trying to tell a story that Lesnar is considering leaving WWE and going to UFC with the Universal title. The hope is that the fans should "hate" Lesnar for doing that as it shows that he doesn't care about the company, the fans or the business and would be dumping on the time honored tradition of dropping the title on the way out.
-- For Reigns, the story being told is that everyone is telling him to step aside after his failed opportunities and that nobody believes in him except Roman himself and thus, that would make people sympathize with him before the match or have admiration for him after the match if and/or when he wins.
Source: Wrestling Observer Newsletter. Subscription information & prices available at f4wonline.com