Benzo's don't come near the bliss and hedonistic, body-orgasmic, and euphoriant properties of the usually more potent opioids (eg heroin, oxymorphone, IV administrated hydromorph). That's why, simple pharmacokinetics. Just look at all the heroin epidemics going/huge increase in heroin-related deaths on the USA recently, people are blowing their paychecks and dying for it, although some GABAergic narcotics are abused for synergism with their opioid of choice.
I personally love diazepam, temazepam, alprazolam and other GABAergics e.g. carisoprodol or etizolam (ETilee, Etizest, Sedekopan, fuck the powder and most shitty or fake blue/pink pellets) in comb. with IV heroin, IV hydromorphone or the few oral opioids that get me off: methadone, oxy.
Papaverium and I seem to have the same hedonistic pleasure in drug cocktails. Although, I also shoot my share of high-quality, bellringer cocaine shots (alone or perfect ratio speedball)