I am a newb to a lot of this, which is why I came to this forum to learn.
Welcome to the weird world of automotive lighting.
Believe it or not, not all vehicles sold in the US are used in/on "DOT" roads/highways/interstates.
True. That's not news.
Those vehicles would not be held to the same regulations on usage or standards.
That is also true. However, it doesn't change the fact that items of regulated vehicle equipment must comply with all applicable regulations if they are physically capable of being installed in vehicles subject to the Federal Motor Vehicle Safety Standards. It doesn't change anything that some of these items of equipment can also be used in vehicles that aren't subject to the FMVSS. It doesn't matter if I'm buying an 1157 bulb for my (unregulated) '57 Chevrolet or for my (regulated) '77 Buick. This was already pointed out further up the thread; I'm not sure if you overlooked it or simply disagree with it (which also doesn't matter; it remains fact no matter who doesn't believe in it). For one example of how this is applied, see
this petition to NHTSA,
this followup letter, and
NHTSA's response to
both requests.
For instance, we have "off road" diesel that is widely sold.
Not analogous. Totally different regulatory structure for totally different material. There are controls in place, though; the penalty for using industrial/agricultural motor fuel in a roadgoing vehicle is
usually quite severe, because it is tax evasion.
We have race fuel that is also widely sold.
...which falls into two categories: road-legal (unleaded and oxygenated -- some ordinary gas stations have this) and not road-legal (leaded). The leaded stuff is very difficult to get hold of, and both varieties are extremely expensive. Nobody's sneaking race gas into the tank of a car they drive with any regularity on public roads, not at $9+ per gallon. Nobody's doing it with 100LL leaded airplane fuel, either; not for many years -- that used to be a thing with owners of high-compression old cars, or racers looking to spend less than racetrack prices for fuel, but a valid airplane tail number has been required to purchase aviation gasoline for at least 15 years. The monitoring is stringent and the penalties are fierce.
But please let's not get sidetracked by the fuel situation which really has nothing to do with vehicle equipment.
There is also, the whole car show/club scene. Where some vehicles are modded to the point where some of them are not even capable of being driven. Most of these have little to do with or care for any shape or form of rules or regulations.
Sure, so that's a self-solving problem: vehicles modded so extensively they cannot be registered or driven aren't causing safety hazards on public roadways.
Unfortunately, the general public is just that, the general public. Naïve and ignorant. You can't stop stupid.
Unfortunately, you're right. All you can do is limit the danger stupid and ignorant people can inflict on others.
you can fine them... if they use non-dot approved items.
There is no such thing as a "DOT approved item". Our regulations in North America do not work on an approval basis.
However, the places that sell these items should have some sort of criteria for limiting sales.
Unfortunately, while noncompliant equipment is illegal to import, introduce into interstate commerce, sell, or (for regulated parties to) install in a vehicle, lots of it gets into the country. It's very easy to buy. Enforcement is up to the individual states, and mostly they don't enforce. Most of their vehicle equipment codes are an outdated, moth-eaten mess. In most states, vehicle roadworthiness inspections (or meaningful ones) are a thing of the past.
Like for instance, race fuel that is sold general is only allowed to be put into containers and not directly into vehicles.
Right...that's a practical measure to help keep off-road fuel out of on-road vehicles. What would you propose by analogy for car lights?
There is no way for the store selling lights to currently know which vehicle or vehicles you are planning to install this on. If you had to give a VIN number or Proof of insurance. I'd imagine sales would drastically drop.
I don't think sales would drop. Everyone who has an (imaginary) off-road-only vehicle also has a (real) registered one. Oh, these bulbs? They're for my '58 VW-based dune buggy I built. Here's the VIN." You really think some shmoe behind the counter of AutoZone is going to care or know enough to say "Wait a sec, these bulbs are 7443s, those won't fit any light installed on a '58 VW, but they WILL fit that '07 Subaru you drove up in! Aha! I caught you! No bulbs for you!"
I wear my seatbelt. But I don't think that the government should tell me to do so. If I choose not to wear my seatbelt, whom am I hurting?
You are endangering everyone around you. Belted drivers usually remain conscious and positioned to control the car after a first collision, so there isn't a second or a third or a fourth. Unbelted drivers usually don't. That's not conjecture, either; this is known and very well documented. It's not about lights, so we won't be debating it here, please and thank you, but the "I'm only hurting myself" argument, while (decreasingly) popular, is based on ignorance.
Sorry for the long post, I didn't have time to make a short one...
Blaise Pascal lives!