Serious question that I'd love feedback on...

In short, why are some women not interested or hesitant when husbands are willing to share them with another man regardless of Stag or Cuck. I can understand the woman feeling the relationship isn't strong enough to take such a risk, that makes total sense. But if it's a strong relationship and the husband is not only on board but the one pushing for it. Why in the world are some women not interested?? It blows my mind because I feel if the situation were reversed most men would feel they hit the lotto. And it seems like over 50% of men wanting this are stuck in the "wannabe" zone. Seriously, I would love a female perspective on this or even couples that have been through this. You would think even the "danger" aspect is gone as most men would help find guys and be close by to protect. I just can't figure out a negative other than not secure enough or flat out doesn't care about sex.
I found this online and sent the link to my wife. She is always gone back-and-forth. She gets super excited about it and really into it. Then suddenly will start thinking. Maybe it’s a bad idea. I think it was more so because she was worried about how it would affect me how I feel about her. After she read the article from the link, I think it gave her a better perspective and definitely helped

 
It took my wife a long time to come to terms with the idea that just because she liked big cock and sex with other men she wasn’t in some way betraying me. She felt that it would threaten my manhood for her to have better sex with sexually superior men. I did not push her and she came around to the idea that her pleasure meant everything to me even if she got that pleasure from someone else.
It didn’t hurt that I confessed that I knew she had cheated on me wife my hung roommate and I was still with her years later.
In our case my manhood wasn't an issue. I'm very small and submissive and she is very highly sexed and needs big cock. She loves to tease me about how good her lovers are while demeaning me. As a submissive I enjoy this treatment so we both get something out of it.