For some reason prenuptial agreements aren't that big of a thing, and I'm not even sure they would hold any water in Europe.
So when I enter a contract with a business, before signing, I know who owes what and what happens if someone fails to provide that. Also, we know what it means to fail to provide. Usually, "Meh, I'm just not happy anymore" isn't a part of that.
So I totally understand people (usually men) not wanting to enter a contract where they face a significant probability of being taken to the cleaners.
If my company fails to deliver a service to a client, or the product delivered is subpar, it's clear what the penalties are.
And those penalties are established upfront. If in the meantime my company goes from a thousand dollar startup to a multi-billion dollar enterprise, I don't suddenly owe an angry client half of what I own. I still owe them what we agreed beforehand, which may be an insignificant sum. Even if it's somehow thanks to them that we became a huge company.
It's my understanding that marriage doesn't work like that.
I am much better off than my girlfriend financially, though. Marriage introduces a financial element wherein I bear a substantial financial liability, in exchange for effectively no likelihood of financial gain. On the other hand, she bears no financial liability, and in fact gains a likelihood of financial gain. No sane person would sign a contract like that with a business. It would be like Amazon buying out a startup with a contract that says if the merger isn't successful, the startup gets to keep half of Amazon.
Another reason contracts aren't analogous is because marriage is an intensely emotional affair. There is no sane way, that I can think of, to make emotional restitution. What's the point of having a contract that's unenforceable because there is no reasonable restitution?
So you end up in a spot where for some people, the benefits of marriage are unenforceable (not that I'm saying they should be enforceable) but the liabilities are very much enforceable. I'm not aware of any common contracts in business, finance or housing that follow that kind of a paradigm.
In business, finance, housing, consumption we are expected to bide by a contract. Yet, somehow partnerships are exempt from this rule.
Could you imagine if startups were run this way? "Hey a legal contract is potentially life destroying for me. So just take me at my word and do this secret handshake. That should be good enough." We'd laugh them out of the room.