#3 Because another high-profile loss could hurt Braun Strowman
Braun Strowman is beyond the shadow of a doubt one of the most intimidating WWE Superstars of all time. However, just like in the case of Big Show and Kane -- who were once regarded as two of professional wrestling's most dangerous monsters, and were eventually relegated to mere lower-card Superstars -- Strowman too could suffer the same fate.
I vividly remember being legitimately intimidated by Masked Kane as well as the 7-foot 500 pound Big Show back in the day. Nevertheless, due to both Kane and Big Show losing one too many high-profile matches, particularly at pivotal PPV events such as the Royal Rumble, WrestleMania, SummerSlam and Survivor Series; their on-screen characters' credibility took a major hit!
Needless to say, the WWE is well aware of the fact that they have too ensure avoiding making the same mistakes with Strowman's on-screen character. Another high-profile loss at an event like WrestleMania, would severely damage Strowman and his monstrous aura...