That's the thing. For some people, it's disturbing, and for others, it's mandatory.
That's OK. I've been with women who ask for that, and got to act as a bull for one in February. Mrs. E doesn't go in for anything painful, and it's not fun for me if it's not fun for her, so no problem.
Then you've got somebody needing to play out some fantasy so badly that he's making up stories for strangers about the "tragedy" where his wife got impregnated during a swinging-related motel rape (this has turned up on here more than once). You can read between the lines that this story is not actually a tragedy to him, but that it would be to his wife/marriage. We all mismatch a little, but it's just depressing to think two people are so disconnected that he's that desperate for an outlet, while she would be crushed if she knew what he really thinks.
That's just my take on it, anyway.