A lot of this however is how it is discussed with the patient. Discussions about the likelihood of there being a real issue when something is seen need to be clear and informative without being alarming. 'We did a routine scan and these often show transient artifacts that turn out to be nothing, but in an abundance of caution we want to do a followup' is totally different than 'we saw something we are concerned about and need to do a followup'. How things are messaged really matters.
Treating MRIs the way we treat blood tests would almost certainly result in huge numbers of needless invasive procedures.