In the US, studies have been shown that physicians who own shares in CT (not so much any more, as it becomes almost 'commodity') and MRI (which is a lot, manufacturers approach physicians to form imaging cooperatives) are ordering imaging up at more than 2 standard deviations from expectations.
As noted, MRIs in themselves aren't harmful. But with prices in the four digits in the US... you can easily pay off your $1.5M MRI machine in 18 months and be printing money with your over-imaging.
But that scan would be limited to the head and not cover the entire body.
I'm also not convinced that MRIs are a great, general purpose diagnostic tool, if it's not used to diagnose concrete issues. The experience of your friend, who I hope recovered from the tumor not withstanding.
So that is why it might be a okay'ish idea to do a MRI scan of the brain every 5 years or so? Depending where you live they are actually cheap and can be paid out of pocket.