The real reasons to legalize:
1) Eliminate a large % of the population from being criminals and teh resulting lack of respect for obeying the good laws.
2) Eliminate the criminal element associated with the prohibition of a substance that has little detrimental effect on society
3) Realize tax revenues as with alcohol. Citizens have the right to create their own wine and beer now but few do it. It will be the same with marijuana - the convenience factor will still cause almost all people to buy it rather than grow it.
4) Distribution and possession of large quantities can still be left as illegal to offset concerns with 2 and 3.
2 and 3 may be true but if you legalize only on the promise of a tax windfall and then the tax revs don't live up to what was expected, what then? Return to the old way? I say legalize just on the pure grounds of personal freedom and liberty and then go from there.
As to people not growing their own out of convenience sake, may or may not be true. In the case of making beer or wine, you do have to make a capital investment of equipment and supplies and then some personal labor is involved. With marijuana, there is still some labor but the capital investment can be very minimal. Marijuana by definition is a naturally occurring weed so all one needs so to speak is a sunny spot and a place to throw out the seed and then nature does the rest. Or is you wanted to go hydroponic or aeroponic, the equipment side is involved but then someone like myself who has already built a aeroponic system to grow leaf lettuce, strawberries, etc., growing marijuana would require lighting upgrades that can get expensive but in a legalized world a small scale system could grow enough product to recoup the cost. Then again, legalizing marijuana in that framework could explode a new entrepreneur class which in our current economy could prove beneficial but I just don't see gov't in our current context allowing that to happen to begin with.
Because marijuana is so easy to grow, making the case to legalize on the grounds of tax revs. is risky IMO in the sense that if tax revs don't meet expectations, we'll just regress backwards. The real tax windfall will come in the savings from the prison-state industrial complex that has been built on the so-called war on drugs.
Besides why given more heroine aka tax dollars to an already out of control drug addict aka gov't?