They move a carrier into a vulnerable position in the Strait, where an attack by a tiny boat could both result in causalities and draw the UK into another protracted war in the Middle East with no clear exit condition and even more casualties?

And for what, exactly, a pat on the back from Trump? (who will then inevitably turn on them after a week and blame them for anything that goes wrong in the war.)

If escorting ship traffic was so straightforward with only upside, the US would be doing it already. Instead of trying to get someone else to take that risk.