If the question is, having a passport while traveling a useful backup idea, I doubt many would disagree.

I always carry a passport just in case I lose my other ID (such as when it was stolen in BUD) or I have a change in travel plans that would require a passport (this occurred once and I was prepared).

However, carrying it just for diversions is perhaps a bit overkill. I doubt most road warriors on FT with many hundreds / even thousands of flights, even with a few diversions, has ever once needed a passport for such as reason. While a small number may have had such a needed, suspect this is very rare, I have not in 50+ years of flying with some 1,400 flights has that need arisen for my travels.