Why is it ok ....

Why is it ok for people on the no-fly list to buy guns?
Why is it ok for people on the terrorist watch list to buy guns?
Why is it ok for people with active restraining orders to buy guns?
Why is it ok for people on mood stabalising medications to buy guns?

Why is it illegal in some states for people on medical Marijuana to own guns?

Below is what would happen if they treated guns like cars:
Why don't people who own guns need to get safety and operation training?
Why don't people who own guns need to get certification to own a gun?
And need to re-certify every few years?
Why don't gun owners need liability insurance for every gun they own?
Why don't people who own guns need to get their guns certified?
And need to re-certify every few years?