Modern marriage =vows? Not always.
While some churches call the bans of marriage "vows", marriages are mostly civil/social contracts both now and in Jesus' time. Even now the spiritual aspect certainly is part of the desired privilege of marriage that same sex couples seek but the social/civil benefit of having legal recognition if paramount: rights of a spouse confers so many practical protections.
Sex was an implied contract of "one flesh" that has long formed a part of a marriage celebration.(Children do not ask to be born yet--who will care for them? Who will claim them?) But it was not necessary(and I understand still is not) for a rabbi to officiate a wedding for it to be legitimate. A dear friend may bless the union. There were witnesses needed, in the main, to note that the couple did indeed go alone into the marriage chamber--the assumption being that two healthy people so attracted to each other would indeed become "one flesh" if left alone for a little while .
Personally, marriage vows that bind you tighter than the personal commitment to one's spouse are bad. They set you up for hypocritical and disfunctional union in the same way as a JW baptism.
Yep--let your yes mean yes. And for goodness sake--somebody take care---lovingly--of the children.
Edit: Sorry, missed your clarifying post--but I agree that the JWs confine two people as much as join them. Not good. Small wonder--that's what their baptism means. They don't let you work out your own marriage or" your own salvation with fear nd trembling".