Why does anyone going through a separation think it is a good idea to remove marital property from joint custody? Family court/divorce judges hate that.

I can only speak for my experience, but my ex took most of the physical assets we shared and the courts didn't give a shit. Tens of thousands of dollars of clothing was considered "her property" not shared property, even though I could produce the receipts for them showing they were purchased with mutual money after we split, because none of the individual clothing items exceeded $1k in value. She also took the piano, valued at several thousand dollars, which we both acknowledged, but it wasn't considered when it came to the property split either. As far as my experience is concerned the only thing the courts care about splitting evenly is your account balances, physical assets outside of the car and house they don't give a shit about.