People give the same reasons for not doing a prenup, divorces still happen, not to everyone, but they still happen statistically.
I used to work for a cambodian guy who organised 'handloans' for the local expat cambodian community. Each memebr contributed $1000 per month, each member had a turn at receiving the tens of thousands each month to use as a deposit etc for a house or business etc. Worked fine until a couple of them refused to pay.
There are so many better, legal ways to build wealth and protect assetts. Money/wealth and trust are not mutually exclusive, however if the other members of a family unit would be so offended by one members wish to protect their assetts, in that relationship, they are seen as one. Just like one spouse refusing to sign a pre-nup.
What are the benifits of purchasing together? What can be acheived that cant be acheived seperately? Why cant you still share a living space, or some savings/ living expenses without sharing everything? What does sharing everything do that seperately cant be done?
This thread reminds me a little of similar discussions on the benifits of Xcoll.