There's a lot of practical reasons why someone wouldn't want one. There are foreign travel and contact reporting requirements and use of weed is forbidden. Some people may be uncomfortable with the level of scrutiny that investigators go through to find dirt on you (talking to neighbors, friends, and family even if you didn't put them down as references). Once your clearance lapses, you have no requirements other than the lifelong NDA you sign regarding the work you did which could hamper future job interviews somewhat if you can't talk about what you actually worked on. If you write a book, you usually need to get permission prior to publishing by submitting drafts to the government, especially if it's relevant to your work.
As for ethics, clearances go hand in hand in working with intelligence agencies, the department of defense, federal law enforcement or a few other departments either as a contractor or government employee. So if you are fundamentally opposed to what these groups do, maybe a job requiring a clearance isn't the best fit for you. There is another clearance called public trust that is very mild that may be required at places like the Treasury or NASA. Basically if you don't want a clearance, avoid working for the government.
I bowed out of the process. I just couldn't quite figure out how to reconcile what was asked of me.
Don't be around people in possession of illegal drugs. Ok, well grandpa died and I know for sure his oxy is in his medicine cabinet. Grandma hasn't thrown that away. You're not really allowed to do that, ya know?
I understand why the rules are the way they are. I understand that they would not care about that situation. The FBI agent asked rather pointed questions about, am I the kind of person who follows the rules when no one is watching. I feel pretty comfortable saying I do. I feel pretty comfortable believing they do not.
There are plenty of smart hardworking people with clearances. I believe in them and I believe they're generally trustworthy, but are held to an impossible standard so they can be fired at any time. I get it, but I can't accept that, so I don't.
For myself it's somewhat ethical, and somewhat practical: there's no way I'd get cleared anyway, due to my history of hard drug addiction in my teens and early 20s. Despite being sober for... gosh, over a decade now, it's a moot point in that process.
They don't really care about the drug use, as much as they care whether you're honest about it. If you tell them one thing but they hear something else when they interview your family and friends, that's a major issue.
What they want to see, above all else, is someone who can't be easily blackmailed. (Which is one reason why homosexuality was a dealbreaker as late as the 1970s.)
Unfortunately, that's not what I was directly told when I inquired, at least for the jobs here in Aus. Perhaps they were just being conservative about it
You might be surprised. I have some friends who did a lot of drugs at one point or another in their life and ended up later holding a clearance. Addiction might be different, but I wouldn't let your past deter you from looking if there was an opportunity you really liked. The clearance process looks more at if you have a problem that can be exploited.
(Now, that said, holding a clearance can be a pain for other reasons already detailed in this thread. A lifetime ban on talking about some things can be an annoying cognitive burden to carry, also.)
Don't assume that your history would be an immediate dealbreaker. With enough time, they are happy to ignore a lot of that stuff. Just be honest.
Of course, if you don't believe in any of the causes you might need a clearance for, it doesn't matter, but don't be too quick to make that assumption either. A lot of stuff gets classified by the government, and not all of it is morally noisome.
Did you miss the several times on the news where whistleblowers had their lives destroyed after speaking up about literal knowingly bombing of children?
As for ethics, clearances go hand in hand in working with intelligence agencies, the department of defense, federal law enforcement or a few other departments either as a contractor or government employee. So if you are fundamentally opposed to what these groups do, maybe a job requiring a clearance isn't the best fit for you. There is another clearance called public trust that is very mild that may be required at places like the Treasury or NASA. Basically if you don't want a clearance, avoid working for the government.