The Royal Rumble is the first big annual Pay-Per-View of each WWE calendar year, and therefore is integral to how the year plays out, especially since 1992 when the winner of the Royal Rumble would either be the number one contender for the title at Wrestlemania or win the title, like in 1992 and in 2016 where Ric Flair and Triple H won the belt after being the last man standing in the Royal Rumble.
As a big part of WWE's marketing push, the Royal Rumble is billed as the start of the "Road to Wrestlemania", and is integral to WWE's winter PPV programming as they transition to the event WWE considers their refresh button. Along with Survivor Series and Summerslam, they make up the WWE's big four PPVs distributed evenly through the year, and these days Money in the Bank making it the Big 5 so that there is less of a gap between Wrestlemania and Summerslam.
While Wrestlemania is the biggest show of the year in the eyes of the company, with the show of shows attracting the record attendance figures for the WWE, with 9 of the top 10 attendance records are from Wrestlemania. This means that a heavy emphasis is put on the building blocks on which the road starts. The negative fan reaction and backlash from the Royal Rumble, such as Roman Reign's win in 2015 and Batista's victory in 2014, led to the company having to scramble and change the Wrestlemania plans along the way for fear of the fan response.
Both Roman Reigns and Batista would lose their respective championship opportunities at Wrestlemania, with Seth Rollins cashing in his Money in the Bank contract during Roman's title fight with Brock, and Batista would submit to Daniel Bryan's "Yes-Lock" during their triple threat match at Wrestlemania after Daniel Bryan was added last minute to appease the angry WWE Universe.
You can see the other entries in this series below: