I think many men take that vow in ignorance, or sometimes with complete sincerity at the time. Which is completely fine. While I do you like the idea of plural marriage, I can also see the appeal of monogamy, and I actually believe that some people (yes, even men), are more monogamous centered than others. Actually some of those men would make great plural husbands, ironically, lol
It seems like the issues with the vows are only a problem when a man later discovers that he wants to practice plural marriage himself. I always feel bad for first wives in this situation. I couldn't imagine committing and bonding myself to someone for what I expect to be a monogamous lifetime, only to have this huge poly bomb

dropped on me later in life. For that reason, I do think that the first wife has a legitimate claim to expect her husband to fulfill those vows, but it's difficult to be so stern about that opinion knowing that men also have a responsibility to teach and lead their wives/families to the truth.
I feel bad for men who find themselves in these situations as well, because I think many of us know how painful it is to feel a calling to or a desire for certain paths in life, while not being able to fulfill or pursue them, for whatever reason.
I really hope that plural marriage continues to be talked about and discussed as openly as it seems to be presently. I've even had positive discussions recently with women who opposed plural marriage, but after discussions with one another they still didn't desire to practice it themselves, however they did come to understand why I support it.
I think it's a slow process, but maybe the generations after us will be more knowledgeable on the subject, and have the ability to be open and honest about what they want
prior to commiting to one another and taking such vows.