So long as travel speeds on roadways are vastly different between automobiles and bikes, I have a hard time seeing how the distinction could be eliminated.
On certain roads, and when groups (of bikes) of a certain size occur, I sometimes see the entire lane taken up by the cyclists. Given the alternatives, it's probably the single safest way to go down that road. For all concerned.
But, outside such situations, as with the typical solo cyclist on a one- or two-lane (per side) roadway, it's utterly tempting (even the one specified legal) manner of riding on that road to keep to the right of the right-most lane. In general, probably safer, particularly in communities or states where full lane occupancy isn't expected.
Trouble is, no matter how many cyclists (solo or otherwise), given the speed differentials there will usually (perhaps always) be at least one motorist who gets "cranked" over the concept of "delays" being foisted upon others. Some will lash out. Some will disregard traffic laws to get past the slow vehicles, perhaps even causing threat of crash to others while doing so. (BTDT, on the receiving end, myself, on a few occasions, where such felons chose to "stick it" to me on the way by, out of sheer sociopathic petulance.)
In the not-too-distant future, I'd like to see every single "major" thouroughfare through a town of any size be required to get constructed with separate, decently-sized bike paths (or lanes), just on principle alone. There's no way we're going to be able to continue handling the sheer number of motor vehicles, without alternatives. And until serious, easy-to-use alternatives exist for the average person, it's hard to change the trajectory we're on. One done, once we build it, I believe they'll come. If forced via taxation and constraints placed on "traditional" motor vehicle access to spots, I suspect that there will generally be a great increase in the percentage of people taking alternative methods ... including bikes. If only the option existed, for safely taking such routes. (Which, quite simply, in many places in the U.S. it simply doesn't, given the roadway designs and traffic patterns.)