[AlbertCory]

It's good to see "what is obvious?" is still one of those evergreen topics, like it's been for 150 years.

Now I have an even better one for you, and I'll withhold my (undoubtedly correct) answer until later:

Wheels on luggage. Why were they so late in coming along? Was it not obvious?

We had aftermarket wheeled carriers for strapping your suitcase in, so people recognized the need. The arguments that "people hired porters or trolleys" and "railroad stations had cobblestone floors" do not hold up at all -- no, they didn't, and airports had hard floors.

You can find articles on this topic. I think they're all wrong. Go.