Z-drugs also cause massive problems with dependence/tolerance, that's probably why. I think they also have a higher risk of alarming side effects. Google the side-effects of Ambien (Zolpidem/Stilnoct), for instance, which include hallucinations as well as various types of behaviour while asleep (e.g. eating, driving). Anti-epileptics such as gabapentin/Neurontin may help with sleep, but their side-effect profile is pretty hefty and they can be absolutely hellish to come off even with a taper, as I discovered this year. I think first-generation antihistamines are relatively safe in this respect, they're sometimes used for sleep. Anecdotally, I'm being tried on various antihistamines at the moment, and while I feel weird on some of them, it's not at really bad levels, and I don't seem to have trouble when I stop them.
Urbantravels - I've known people have far more trouble getting pain meds for acute use than I have for repeated medium-term use, actually. My mother had eye surgery a few years ago. The eye specialist had refused to discuss the horrendous eye pain she was in, he just kept on telling her that his surgery would fix it. When he operated on the first eye, he told her a very complicated drug regime orally, shortly after the surgery when she was woozy and in no fit state to take it in. It turned out that he'd undermedicated her for pain. Eye pain, I should mention, can be one of the worst types of pain. So when the time came for him to operate on the other eye, she very sensibly asked whether he could give her the medication regime in writing this time, at a more sensible point where she could look at it clearly, and also mentioned that she'd been in a lot of pain despite the meds for the previous op. He promptly threw a hissyfit, threatened not to do the operation, and wrote to her GP accusing her of drug-seeking. I can't remember how she sorted this out, but she did have the op in the end. After a while, we realised that her eye pain was still pretty bad. The eye hospital did not want to know. So I think some of the problem may be that certain departments absolutely do not want to admit that their patients have serious pain issues, let alone to deal with them.
Similarly, when I had acute calcific tendinitis, which even doctors call "excruciating" (and you know how they underplay pain), I spent two days ringing NHS Direct and being told, "Ooh, you probably shouldn't take that much co-codamol, dear, that's quite a strong drug," before I finally got someone who had the sense to realise that the pain I was reporting was extreme, and told me to go straight to hospital. And even then I was very lucky to be given pain meds while I was waiting (I'd originally gone to the out-of-hours service and ended up in A&E for 8.5 hours), got a diagnosis, didn't get the treatment they recommended due to miscommunications, did at least get some pain meds (co-codamol and tramadol - I was stoned off my face for a month, which was better than being in that horrendous pain), and had fairly lousy handling of the side-effects.
I didn't get dependency problems that time when I was on the stuff for a month, but the next time I had a bout of calcific tendinitis and was on co-codamol for a month, I had about a week of withdrawal when I came off it. Not too bad as such things go, jittery and insomnia. The GP I spoke to told me that co-codamol doesn't cause dependency, which is utter nonsense, it's an opioid for heaven's sake. Either they're handing the potentially dependency-causing drugs out like candy, or they won't let anyone at all near them. Good management of risky drugs like this is far too rare.
By the way, there is a huge number of people who are prescribed benzos, Z-drugs, opioids or similar for purely physical issues (pain, sleep etc.) who end up not just physically dependent, which can be horrendous enough, but psychologically addicted too.
