#4. Roman Reigns vs. Daniel Bryan helps grow Jey Uso's heel character
WWE now has Jey Uso as Roman Reigns' henchman and while his cousin joining him was a bit of surprise, it doesn't constitute a full-blown heel turn yet. That's why WWE needs to test the limits of how far Uso is willing to go for Roman Reigns and use that as a sort of payoff for fans.
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For example, let's say it's the final minutes of Daniel Bryan vs. Roman Reigns and the referee suddenly gets knocked out by accident. Reigns then instructs Uso to grab a chair and give it to him. This gives WWE a chance to do a 'will he or won't he do it' moment to hook fans on.
In the end, WWE obviously has an interest in patting this out as long as they can, which is why this trope is so needed. If nothing else, it keeps fans wondering what will happen next, makes Reigns look even more like a heel, and creates a great deal of sympathy for Bryan.