FWIW, as a cyclist I would love to see Idaho stop legislated. As a driver, I do not follow stop rules blindly. If approaching all-way stop a see a cyclist (or anyone) close enough to the intersection without any signs of the slowdown, of course I will let them cross first. But even with the Idaho stop legislated many cyclists misunderstand it. For example, Idaho stop means treating stop sign as a yield sign, which means if you can safely cross the intersection without impeding anyone else (e.g. if there is no one else around or they are far enough from the intersection), you do not have to stop. It does not mean "I don't have to stop and have priority over cars no matter what".
That is exactly the point of making something the law instead of informal rule - there should be no ambiguity.
A compounding factor is that while rules for cars are more or less standard throughout the 50 states, rules for bikes are a complete mess. For example, in Massachusetts, a bike can ride in the left lane (I mean, you should probably have a good reason but it's 100% legal) where as in some other states, bikes have a mandated max distance from the right hand curb. How can anyone know what is actually allowed?
And a solution to the disjoint sets of laws is that states are very different. Super urban areas necessarily need different laws than very rural areas. Even regional snow fall amounts is a factor as bike lanes basically disappear in the winter.