In the social network of users, some will sell on a large scale, but typically not for a long period of time, as it is a hassle. The only real organization in drug dealing is at the higher levels where the drugs are purified, smuggled, and cut. Furthermore, ignoring empirical facts, the image of the pusher is pretty unsound. It only makes sense to spend time hooking people if you plan on selling to them for a long time and they will not be able to go elsewhere. Neither condition tends to be true.
Addicts are notoriously unreliable customers.
Furthermore, as I have already mentioned, it is difficult to get hooked on H. Addiction is rare within the first 6 months of H use. So, you'd have to be giving out samples for a while before you had an addict customer. Finally, associating with non-addicts is the surest way to get busted.