Hubby tried for a couple of years to be my Dom, to the extent that he set a boundary that he would prefer I not engage in any type of kink or BDSM with any other partner.
But after a little while, it became abundantly obvious that he was, as he put it, "playing Dom." Which didn't do a blasted thing for me; I wanted to actually submit to an actual Dom, not play make-believe with someone who admitted the whole thing made him feel silly. And yet even after we agreed it wasn't working and decided not to bother with it anymore, he still refused for a while to budge on the "no kink or BDSM with others" thing; at that point, it was less about treading on his toes and more about his fears for my safety.
I finally got that sorted out with him this fall, after having a very brief FWB thing with a guy who wasn't into BDSM but had some other kinks that intrigued me. I reminded Hubby that he's known all along that I skew submissive, and that he's known I have some interests that he doesn't share when it comes to sex. I also reminded him that the latter fact was the entire reason he suggested opening the marriage three years ago, and that by being unwilling to be my Dom but also unwilling to let me explore with anyone else, he was once again forcing me to choose between cheating on him or letting him define my sexuality.
(I know some people here are going to say I'm an autonomous adult and can do what I want, which is true on the face of it... but doing what I want in direct opposition to requests from Hubby would lead to far more stress and marital discord than I'm willing to cope with. He doesn't control me, but I do generally choose to either negotiate or give in to what he prefers rather than telling him to go fuck himself and then doing whatever I feel like doing. And he gives me the same respect.)
The outcome of the discussion was that he agreed that it was unfair of him to prevent me from exploring something I felt I wanted/needed to explore, so he agreed to the idea of me finding another Dom or someone to explore other types of kink with. In a case of "coincidence", I met Woody within a week of that discussion.
During the time that Hubby attempted Domness, aside from the obvious issue of him not really being into it, the problem I had was fear of him judging me. This is a fear based in the early years of our relationship, when he was judgmental about a lot of things I wanted to try sexually. It's far easier for me to explore and experiment sexually with someone else, because they're less likely to judge me and because if they do judge me, I can tell them to go to hell, whereas due to finances and other constraints, I can't just walk away from Hubby.