Should the reason for using homegrown marijuana make a difference in Congress's Commerce Power?

I’m not at all surprised by the Supreme Court’s opinion in Gonzales v. Raich. Justice Stevens, writing for the six-member majority, relied heavily on Wickard v. Filburn, a 1942 case that upheld the regulation of a farmer’s production of wheat that he grew for use on his own farm and never intended to sell. The Wickard Court interpreted the Commerce Clause to allow regulation of the entire market on the ground that even trivial components on the market count, because, taken together, they have a substantial effect on interstate commerce. Home consumed wheat was part of the market both because it supplied the home-use needs of the farmer who would have had to buy it in the market and because the farmer might change his intentions and decide to sell it in the market.

Under the 1995 case, Lopez v. United States, which struck down the Gun-Free School Zones Act, there seemed to be some reason to think that a completely noncommercial activity might be treated differently from a farm, but Lopez did not involve regulating a market in a product, but individual gun possession.

Justice Stevens wrote what I thought the Court would have to say: if noncommercial, homegrown marijuana were seen as beyond the Commerce Power for medicinal users, it is also beyond the Commerce Power for recreational users. The theory is the same, that noncommercial user-producers can’t be included in the Wickard-style analysis. Justice O’Connor, dissenting, joined by the Chief Justice and Justice Thomas thought the two motives for growing and using marijuana are “realistically distinct” and for that reasons susceptible to different Commerce Clause analysis.

But why? O’Connor is giving affirmative force to the state’s interest in conducting it own policy experiments. But what if there were a state interested in performing the policy experiment of authorizing the recreational use of homegrown marijuana?

UPDATE: Justice Thomas distinguished the medical use from the recreational use because the state statute, California’s Compassionate Use Act, defined and controlled who could use marijuana. This would mean that Congress began with power to reach homegrowing medicinal users of marijuana, but lost that power when California set up its regulatory scheme, because the state regulation drew a crisp, new line. Does anything else in Commerce Clause jurisprudence work that way?