here's the thing--making a PFD law would be a monumental waste of time, money, and resources to get it proposed, passed in the legislature, written into regulations/code--then enforcement becomes a pain in the ass encounter between boaters and johnny law--not to mentioned an additional unnecessary source of friction. Then the only people who will comply are the cognizant, aware boaters who would comply anyway, and the tubers/cut-off jeans, sneakers, mullet-headed crowd will flout the law anyway, and a percentage will still drown/need rescue just like now, so nothing will have been gained, and a huge effort and resources will have been wasted.
I believe education and awareness campaigns are the only way to get the idea across--people just want to have a good time on the river, but underestimate the river and pay for it with their lives. If people were as aware of the power of the river as boaters/rafters are, I don't think they would think it was so "uncool" to wear a PFD.
but what we don't need is another law, or amendment, or ballot intiative, or referendum, etc., ad nausea...
that's my opinion anyways, hardly even worth $0.02