People are going to use drugs regardless of legality. There has been great harm to individuals from ingesting substances of questionable purity. Legalizing cannabis has allowed adults that choose to consume get consistent quality and avoid sketchy circumstances when purchasing.
As for society as a whole it costs less to help people that abuse drugs than it does to imprison all drug users. We should not punish adults for what they choose to put in their bodies on their own time.
It would probably be helpful to define abuse of drugs as not being able to function in society as a result of use. The clinical definition of using more than the prescribed dose isn't very helpful. Depending on the drug a higher dose can be desirable for different reasons.
If somebody wants to check out of society I don't want to stop them. That is their choice. But if they are trying to participate in society and struggling with drug abuse we should try to help them.
Some, not all. You can see escapist users with nearly all drugs that provide it. I have encountered users that are consuming because they dont want to feel anything at least for a little while, to "check out". But most users of a variety of drugs are doing it for entertainment or experience, to enjoy living.
As for society as a whole it costs less to help people that abuse drugs than it does to imprison all drug users. We should not punish adults for what they choose to put in their bodies on their own time.