Why doesn’t tile last forever? I’ve heard about the tile in European cathedrals and Oriental palaces that has been there for centuries. Why is Marazzi warranted for one year?

This question directly relates to question #3 above. A tile’s ability to withstand wear is determined by many factors, i.e. glaze composition, surface texture, traffic levels, maintenance procedures, etc. Marazzi’s standard limited warranty addresses the issue of a tile’s conformance to industry standards regulating First Choice products. Any variation from those standards would be evident within a one-year period.
 
You can bet that the tile in those ancient installations looks much different now than it did when it was installed. More than likely, the edges are chipped; the surface is scratched and worn (in many cases through to the body); there are impact chips and structural cracks - all of which may seem acceptable in an historic site but less so on your kitchen floor!