The way I personally see “for better or for worse” is if for example something happened to my husband and he became wheel chair bound or otherwise incapacitated I’d not abandon him.

Other people understand it as if my husband became a liar or treated me badly or decided to live off me and take advantage of me, well it is not included in my “for better or worse”.

And if people stay in abusive marriage because of their vows, then their vows must have included “I promise to endure abuse”. My vows sure didn’t include that.

I think it depends how one understands “ for better or worse”