because fankart
phrase explanatory
Used to convey that personal desire is a/the justification for an action.

ORIGIN early 21st cent.: because fan + kart. Referring to the MIT produced shopping carts mounted with ducted fans that lacked any obvious function.
As an alternative to "because I want to, damn it":

A: I don't understand your obsession with building 3D printers when better ready-made ones already exist. Why do you do it?
B: Because fankart.

A: What are you working on today?
B: An electric scooter. And I'm making my own motor controller because... well... because fankart...