Hellraiser hellraises a lot of questions. Why would anyone want to use something that brings infinite pain? How is this infinite pain also infinite pleasure? Does Pinhead sleep sitting up? Most of these answers can be found if you stop looking at Hellraiser as a horror movie and instead watch it as a metaphor for drug addiction. Let's start with the satanic Rubik's Cube Frank uses to summon the Cenobites, the Lament Configuration.
Entertainment Film Distributors
Frank buys the box from a shady dealer -- the same kind of person you would buy a fake Charizard holographic card from. Or, you know, drugs. Because the Lament Configuration is an addictive drug. Frank uses the box knowing his soul will belong to the Cenobites. He needs the pleasure. Later, when Frank's niece Kristy throws the box out a window, Frank loses his mind. This is the same box that's doomed him to an eternity of torture, but he still needs it. He's going to use it a little bit, you see, just to take the edge off ...
The brothers are two sides of the same person. Boring ol' Larry represents sobriety, while pervy Uncle Frank represents addiction. Julia, Larry's wife, is a classic enabler, only instead of bringing Frank drugs, she brings him dudes to kill so he can become "himself" again. Eventually, Frank kills Larry and starts wearing his skin, which is the moment when addiction has taken full control of his life. Frank's demons (the Cenobites) finally catch up to him and tear him to pieces. The addiction has won.