A suit with an extra pair of trousers?

photo source: Ralph lauren Black Label winter 2007 collection.

Unless you go custom made or bespoke it is very difficult to buy a suit with more than one pair of trousers. Trousers are exposed to more wear and tear than the jacket so having an extra pair can extend the lifetime of the suit. In these days of eco awareness, I wonder why nobody is bringing this to the table.