They raid the cannabis clubs because under US legislation the federal government supersedes the state. The taxpayers who voted to legalize it for medicinal use in California are watching their federal tax money go to the DEA who then comes in and refuses them their medicine. And this isn’t even the worse of it. Incarcerations are up twelve-fold since 1980 for possession of marijuana charges.
People use marijuana to relax and instead get throw in jail with hardcore criminals. This negative influence experienced in jail is no good for society in general. Imagine if everyone who ever tried thc was thrown in jail. Over a third of the US population would be stuck not only draining tax dollars but being negatively influenced by criminals. Hemp is an extremely valuable cash crop that is not legal to grow.
It is unfortunate to realize that the constitution was signed on hemp paper, but the government is so scared of the plant that it is not even legal to grow now. The plant can be turned into clothing, paper, rope, and fuel. Currently we import all hemp from other countries.