It's the unknown.
Two men, one ring and millions worldwide baying for blood.
That is why this week's announcement that Floyd Mayweather, arguably boxing's finest ever technician, is to come out of retirement to face the brash and bombastic face of the UFC, Conor McGregor, has garnered such attention.
Boxing purists, as I like to consider myself, know that this is a mismatch.
Nothing more than a money spinner.
Sure, in an octagon McGregor would defeat Mayweather with ease.
But in a boxing ring, Floyd is king.
And 'Money' Mayweather will live up to his name.
He's reportedly guaranteed a cool $100 million.
While McGregor's hardly picking up chump change with $80 million going his way.
Both will inevitably earn even more through a cut of pay-per-view sales and sponsorship.
How can they command such enormous purses?
Simple.
Through our love of the most basic and barbaric form of competition.
The noble art of boxing-or, the ignoble art of damaging the human brain that has enthralled us for generations.
Should Mayweather dispose of McGregor, which anyone with an ounce of boxing nous expects, he will overtake the legendary heavyweight Rocky Marciano with a record of 50-0.
Another statistic that will make boxing purists wince.
But, whether we disagree with the ludicrous amount of money both men will inevitably make for punching each other in the head, or simply see this charade as irreparably damaging the reputation of both sports, the majority of us will look out for the outcome.
It's our morbid sense of curiosity that will financially secure both men for several lifetimes over.