#1 You pay to see him
Let's face it, other than Cena nobody else gets a reaction like Roman Reigns whether he's in the main event or not. He's not a top draw yet but he's well on his way to becoming one. He's marketable, good looking and athletic.
Kids love the superman persona, women love his dashing looks whilst the men label him as Cena 2.0, either way, there's interest in him. Memorable moments are created when the crowd are invested in the talent.
Breaking Vince Russo and Jim Cornette update HERE.
You can have as many 5* WRASSLING matches as you want but if the crowd don't care, nobody will remember it. Think of the most memorable moments of in recent WWE history, Reigns has been in them, why? Because like it or not, people are invested in him whether it be hate or love.
At the end of the day, the WWE needs several main event players in order to increase house show attendances, PPV buys and network subscriptions. There is room at the top for other stars that aren't necessarily your favourites.
Don't be selfish, leave Reigns alone.