Well you can have a superconductor with no current running through it. Just charge the electromagnet with current during the scan, then bleed it off gradually when you're done. No need to turn off the superconductivity to power down the magnetism.

MRI magnets are a pain to setup. It's not an easy task.

I can remember when the NMR (superconducting magnet as well) in our school "quenched". It's a hell of a lot of current to dissipate.

Need to get some tech from Germany to come out and power it back up.

And $75k ish of helium - which is getting pricier by the day, and can at times be impossible to source. And the riskiest time in terms of quenches, is during ramping. Our last quench re-occurred just as they finished ramping it. We were down for 3 weeks ish and the cost excluding helium was huge.