"Chris intended for Scully and Mulder to be platonic!" "Scully and Mulder clearly have feelings for each other!" IT DOESN'T MATTER. There was never going to be anyone else. They are stray cats bonded who cannot be adopted seperately.
Your spouse should be the most important person in your life. Unfortunately for anyone trying to date them, that slot's taken. They've been through so much together, so much that cannot be explained, either because of how fantastic it was or because it's classified. By the end of Season 1, Mulder is admitting that she is the only person in the world he trusts. Midway through Season 1, Scully confesses that he's the only person she'll put everything on the line for. And every single episode after it hammers that fact in. Mulder sacrifices his noble quest for the truth over and over again to guarantee Scully's safety and happiness. Scully sacrifices her career, her reputation, to become Spooky right alongside him, without even really believing in aliens. She's seen them, she just doesn't really care that much. Not like Mulder. But Mulder is obsessed with them, and so Scully will devote her life to them.
Every single time Scully gets kidnapped, she's on the phone with Mulder. And it doesn't matter if Mulder is miles and miles away, she ends that message begging him for help. And every single time, he comes.
Mulder was always going to be alone. His quest was too important, his work so all-consuming, that there was never going to be a nice normal girlfriend, especially since the women he loves have a bad habit of being abducted. Scully tries to date, but they all pale in comparison to the danger and thrill and perhaps even purpose of her job.
They also just like and respect each other. In this current atmosphere of enemies-to-lovers that's just people being jerks to each other, it's refreshing to see two characters who genuinely enjoy the other's company. Scully and Mulder fundamentally disagree about the place of the fantastic in the real world. But he is always asking her what she thinks. He firmly believes she is the smartest person in any room she happens to walk into. Scully trusts him beyond reason, maybe not jumping aboard his theories, but never tearing them down to others.
On top of all of that, Mulder is playing with her necklace. His hand is on her lower back. He makes her crack a smile. She's burying her face in his shirt. He's kissing her forehead. She's bumping his shoulder. It is the most sexual tension that has ever been captured on film. They want each other so badly, with so much yearning and tenderness, its simultaneously painful and glorious to witness.
TLDR; it doesn't matter if it's romantic or platonic, Scully and Mulder are the most important people in each other's lives, bar none.
