I think you have to weigh the choices and risk involved. What's the chance of a small envelope containing 500mg, that's machine sorted, being pulled off the line and opened? What happens if it is? It's not a trafficable amount, though i'm sure they could charge you with some customs related offence, plus possession. But what happens when they pull this envelope and find the 500mg of whatever? The name won't match the address and the address likely isn't the residence of the real buyer, who's they don't know. So, no name, a small amount of drugs, and perhaps no address? And even if it is the address, how are they going to prosecute that? You can't prove someone ordered them. And if it wasn't addressed to them, you can't prove it's theirs. You can send anyone anything. If someone sends me a letter full of anthrax, I'm not liable for it.
I'm not saying I condone doing this. But it's certainly not as black and white, nor probably reckless as you make it sound. If anything it works out better for everyone. No proceeds toward crime activity from buying through dealers + local suppliers. Much much higher chance the goods will be as advertised and unadulterated, which lowers the risk of overdose or complications. It's almost like a trial of decriminalized drugs. The store is very much what you would expect from a legit industry with competition. High quality goods, and low prices. Customer reviews for peace of mind.
They never will, but the government should be welcoming something like this. It's taking drug related crime (in relation to its local production) off-shore and the harm minimization effect flowing on from good quality stuff.
But anyway, ordering drugs through the post is a generally bad idea. But there's more to it.