Because they have a fixed yield and lack the upside of typical shares. Higher interest rates = higher required yield. How do you increase the yield of bonds or pref shares already in the market? You lower the price.
It does create the potential for national insurance companies and remove barriers. I wouldn't be surprised to see a few upstarts target younger consumers with lower healthcare needs and a higher bar of service. How will they overcome these problems? I'm not sure, but that will be their competitive advantage. Maybe target urbanites and contract with one brand of urgent care centers and one hospital network.
I bought into bonds thinking that they'd be a good Vol hedge if Trump won. Turned out I was wrong as the markets decided to imply a rate hike. So got into XIV this morning and out by mid day for a 5% gain. It's a shame, could have walked away with 10% if I had been a bit more patient. Didn't get as many shares as I wanted either.