The context is the British pharmacy "Boots" - think Walgreens. The parent commenter's argument is that our society at large does not want heroin and coke sold at the corner drugstore. They want these substances out of sight, out of mind.
It's all very well for us to imagine legalized drugs would be safer and more easy to regulate, but a majority of people disagree - so for the time being, they will continue being sold out of the boots of cars.
