Is a brick supposed to be a kilo? If it's just a pound, a duffel bag for dope makes sense. (At the risk of the bag bag slippery slope meme becoming real.)
Either way, the way it works now is pretty fine. There's no real reason to need to put it in a bag on its own. There is supposed to be a risk involved in doing these things. That's why it's so profitable.
Guns definitely made sense because some can be seen just from holding it. Drugs don't show up in your hands when you carry them, so a bag is completely unnecessary. The point of gun bags was not to carry more, but to be able to conceal a single gun you carry. As a matter of fact, gun bags typically take up more room than the gun it's concealing in your inventory.
Just be glad nobody can physically see what you're carrying.