... and create a new opportunity to do a denial-of-service attack on any person by reporting her phone number as a source of unwanted calls. If the reporting happens via a web page this DOS attack can be automated and sold as a service.
Lead is used in brass for corrosion resistance even in handling drinkable water. It does not markedly leach into the water and increases the usability of the plumbing from less than 5 years to more than 30 years.
Gas welding the material results in lead fumes. There is a big quarrel about the usage of lead in water pipe connector brass parts going on in the EU.
MR imaging is possible with permanent magnets and resistive (copper wire wound) magnets at low field strengths, below 0.35T or so. Above that the heating of the magnet windings becomes excessive and it would be very difficult to maintain a stable enough field strength.
Superconducting magnets are very nice as long as there is no quenching. The material used for conductors must be mechanically stable and perform consistently from one production batch to another. One reason why current high tc superconductors are not popular...