However they don't explain why we should believe that current dealers would be willing to start collecting and submitting taxes to the government. They already have a product that they are selling tax-free, what is the incentive for the dealers to start charging more for the same product?
You just assume dealers would still be selling it on the street. Do you see any alcohol dealers on the street? Any tobacco dealers trying to get you to buy a smoke? When something is legalized it gets controlled by the FDA for purity and sold in stores. Excessive profits are taken out by competition and dealers either get unemployed or find a job somewhere else. Learn some basic economics, FFS.