It is for a very small percentage of the population - namely those people who keep vehicles 10+ years in high salt climates and don't inspect on a regular basis. But a non-issue for the vast majority of us. Even my 40 year old vehicle has very, very little rust on even the uncoated mild steel components.

Personally, if legislation is determined to be the answer (and I don't think it is...):
Rather than requiring higher cost materials for all, I would prefer legislation to force people in high risk areas to inspect and repair their vehicles. There is a lot more at risk than just brake lines. Or take to the Japanese extreme and require replacement.