The ability to potentially obtain a product of better quality, and to not have to deal with such shady people to get their dose.
No, we should be making it much harder for them to do so.
It's all the crap it gets cut with by shady dealers that kill people.
Opium may be addictive, but given its low potential for overdose it is highly preferable for addicts to use opium as opposed to oxycodone, heroin, fentanyl, carfentanyl, etc.
We've proven over time that 'get people to stop doing drugs' isn't a viable end game. It's not going to happen.
The best we can do is harm reduction, at least in this case we can stop people getting fentanyl, thinking it's oxycodone or heroin, and OD-ing.