Unfortunately this feels like situation where the free market will fail to incentivize the best solution. The airport itself does not feel the economic pain from its travelers getting sick from touching its steel surfaces. The passengers likely aren't even aware this choice might have caused their sickness. So airports will always choose steel over copper/silver/brass so long as steel is cheaper.
This seems like a reasonable place for regulators to step in.
This seems like a reasonable place for regulators to step in.