Thing is, the way our government works, they will never legalize all these relatively harmless drugs, we are at a time when they are slashing public spending and privatising off swathes of the NHS.
You only have to look at their existing policies for harmful drugs such as nicotine and alcohol, which is, collect taxation, regulate sale to minors, ???, ban some advertising, profit....
It's absolutely woeful, you'd have to revamp the NHS to support more drugs awareness, treatment, distribution, allocation, and rehabilitation to a meaningful level, as introducing more substances that are taxed and regulated would cause the whole system at breaking point already to collapse. Which would take money and effort the government aren't interested in, they just want to cut spending and increase economic growth in the most efficient and conservative manner.