Again, a lot of advice from people with little to no first hand experience owning steel boats, repeated over and over.
The most recent steel boat we owned was built in 1978. It was built before the "better" epoxy coatings were widely available. It was built without proper limber holes in the stringers to provide drainage. It had stainless welded directly to the mild steel, at right angles and without fairing compound, so the paint had little chance of adhering well. It had places in the interior that were inaccessible without a hours of work disassembling the furniture. It had lazy owners that would rather sail, watch whales, drink wine.... than maintain the hull. It had rust. We kept the boat looking good, but there was always rust creeping out somewhere.
All that said, the boat is 40 years old. Every 5 years we paid for a complete ultrasound for insurance, and every haul-out I personally sounded the hull in suspect areas. Hull wastage never measured outside acceptable limits, and there were no areas that had been cut out and replaced, so this was all original plating.
40 years with hard use and marginal care, and there was nothing that posed a threat to hull integrity. You can say that this is just one example, but metal boat owners talk a lot to each other, and this was pretty much the norm with everyone we interacted with. Keeping up with rust and corrosion is no big deal. You want to scare the shit out of a metal boat owner, start talking about stray current. That and resale value are the only two realistic downsides to a metal boat.