>>5082621As a weirdo who's into it, there's a lot of parts to it. it doesn't apply to everyone and not every single factor is involved in its appeal.
I never got tied up as a child. Even when being beat up or pranked, or in accidents, I have never been restrained. While adolescence can develop people, the level of Freudian sexual causation is almost universally agreed to be false.
Common interest of SM: There's a loss of control or gaining control. Usually the people who gain the kink late are generally due to the desire to relinquish control or gain it. It's not even necessarily power, but can also stem from responsibilities, whether to lose it or gain it on another person.
The loss of motor control also leads to heightened senses because there's nothing else to draw the tied up person's attention. Further sensory deprivation can lead to interests blindfolds, mummification/latex based restraints.
Finally there's bit of a dying notion that it's wild and kinky. Media both pornographic and non-pornographic has kinda skewed the perception that being tied up is a super deviant sex kink thing that's secretive... yet everyone knows about it. Bondage and oral sex is this kind of weird litmus test of slutty v prude in the public eye and it kinda gets referenced or people experiment with often for that reason.