Well, when it comes to anti-OWB laws, I would say that New York and New England were the prime areas for that, resulting from a lot of dis-information being posted and stated about them, leading to state and regional OWB bans and EPA regulations. New York State had an official air quality web site that showed several OWBs that were obviously staged and burning tires and green wood, and stating that they were typical OWBs and that they were evil. That site has since removed the photos, but it was obviously a political ploy to get EPA regulations on OWBs.
As for states passing laws, what is good for some areas may or may not be good for others. Air quality is an issue here in many areas in the west, and for specific reasons. Mainly we get winter inversion air layers and the coastal valleys get choked up with smoke and smog at the lower elevations and it gets trapped there for days and days. So they have burn ban days in winter when inversion layers happen, to reduce the smoke in particular areas. Why that would cause the burn bans to spread to other areas that do not have that issue is beyond me. The banning the sale of non-EPA stoves and removing older stoves when homes are sold seems to stem from the Central Valley in California and Washington state, where winter inversion layers are the most common. I am not happy that Oregon mandated the same requirements, when they allow nurseries here to burn live green trees for months on end in winter, with zero restrictions. Its a hypocritical world of politics. Like OWBs, old stoves get a lot of the blame, but in fact have little impact on air quality overall (at least here in the US west). OWBs are actually so few in number here in the west it is absurd that Washington state banned them outright, but politics is like that. They picked up on the New England rants (and dis-information) and passed laws.
Many of the studies and reports I've seen indicate approximately 1.5 tons of PM per heating season. I suppose some states simply are trying to stay ahead of the game by not letting the devices accumulate. When you think about some Midwestern states and the thousands of OWBs installed, 1.5 tons each does impact the breathing envelope, especially where there is an accumulation of the devices. Although many state DEQs know this they are constrained by state politics. However, some have covered their bases by listing OWBs as a potential threat in their implementation plans just in case somewhere down the line federal air standards are exceeded and tier 1 problems alone can't fix the issue.