So if you have abnormal findings in 10% of patients that merit follow-up scans, you can trivially do a series of 3-4 scans without affecting the overall cost too much.
Doctors simply need to get out of the headspace where MRIs are extremely scarce tools of last resort and treat them like we treat blood tests.
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.