Some more background / history on Nevada.
None of this is meant to be political; it's simply meant to give you an understanding of the hows and whys.
Nevada traditionally is a very conservative live and let live state. Rural Nevada tends to be populated by people who don't like other people. The only reason why there are other people there, is because they are other people who don't like other people.
For years power centered around Northern Nevada but as Las Vegas grew power shifted to Southern Nevada. The people moving to Las Vegas, and to some degree Reno, typically came from states that more legislatively constricted (California & New York) and as such Nevada become more tolerant of more legislation.
Next the landscape of Nevada
Only 2 of the 17 counties in Nevada require smog; those being Clark (Las Vegas) and Washoe (Reno). Nevada has a large amount of federally owned land and is fairly reliant on federal dollars.
The Las Vegas valley has bowl shaped topography, as well as a diamond shape with mountains on the three sides (the passes are at the points) and this results in pollution being trapped in the valley. This results in high pollution days; Nevada basically started the smog checks (some 35-40 years ago) because the feds threatened to withhold dollars.
The Nevada Legislature and how we got here
The Legislature meets every other year and passes a 2 year budget. For years the cars built before 1968 (I think) were exempt; this was never updated so the legislature passed the classic plate laws. Fast forward to now and the problem is a Las Vegas problem; the legislature is now dominated by Las Vegas area representatives, who as I've pointed out, tend to come from areas where more legislation is the answer.
The reality
The reality is that we are talking about a maximum of 1500-2000 cars that are not running properly and using the classic plate as a way to get past smog. Even if you took these cars off the road, there would be no measurable difference in air quality.
The problem is mostly a PR problem; if nothing is done the state risks losing the federal dollars it needs to make road repairs........and so the change in the current legislation.
The simpler task would be to crack down on the abusers but the state lacks the resources to do that. The revised legislation, ironic as it may seem, is the most expedient way to solve all the issues. It keeps the feds at bay and puts the onus on owners to ensure they vehicle is compliant.
Also note; while I'm not in favor of the revision I do understand it.