plenty of conservative peers are fighting to end the drug war and return power to the states.
If you mean a true Conservative, as in "small government", yes. In that respect, even I am a conservative. But, the vast majority of "conservative" politicians are social conservatives, AKA Authoritarian Liberals. Such liberals are typically not trying to end any government spending.
Drunk Driving kills a lot of people, and so why exactly would we want to add to that by encouraging the use of pot?
Studies have shown that people who are going to DWI will tend towards Marijuana instead of Alcohol, if it's legal. Marijuana does impair your driving skills, but not nearly as bad as Alcohol; statistically, marijuana's availability
reduces rates of traffic accidents.
Why Medical Marijuana Laws Reduce Traffic Deaths | TIME.com
If we could just magically "make" all drugs go away, then we would, but we can't. Prohibition is ignoring the problem, while regulation deals with it. In Portugal's case, they decriminalized all drugs, and still found it to be less harmful than prohibition.
Decriminalizing Drugs in Portugal a Success, Says Report - TIME After allowing everything from Marijuana to Heroin, they found that all use dropped, addiction rates dropped, STD rates from needle sharing dropped, Overdoses dropped, total drug related deaths dropped, and teen drug use dropped. It was a complete success. We've seen similar success stories from dozens of countries that have started to reverse drug prohibition, and it's most noticeable for Marijuana.
All places that have legalized, regulated, or decriminalized Marijuana have found that all negative things associated with it start to reduce. Prohibition is the cause of the harm.