I'm pretty sure most of us feel this way. I don't even take advantage of the Plat's 5X points on airfare because I want the included travel insurance provided by other cards I have.
But many have long suspected that it is in fact the reason that Amex separately sells travel insurance that is precluding it from being included with the Plat/Centurion.
A likely explanation, except who is buying travel insurance from Amex? I'm not being facetious I have never even thought to look them up when buying trip insurance; do they even sell to the public or are they reunderwriting from the cruise lines, Travelguard, etc?