[wildzzz]

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.