Mars is an example of why the natural process isn’t exactly reliable either… You can engineer things to be as durable as planets, there’s just generally not much demand for a project to be that costly in resources. In this case, I’m pretty sure making an artificial magnetic field that’s more durable than the natural one would also be cheaper than recreating the natural one.
… Silk is used as a cold weather baselayer in active wear? Not sure if it performs differently as an outer layer, but it’s got solid insulating properties for keeping in heat