The only viable target for a hypersonic missile is an aircraft carrier. It would be stupid to waste a hypersonic on a tanker or cargo ship.
Destroying a cargo ships with missiles is the whole point. Every successful attack is driving shipping insurance through the roof. Shipping insurance for cargo ships is too expensive or not even offered and now most cargo ships are going around the horn of Africa instead of through the Suez Canal thanks to the Hooties. Also the Hooties can place their bets on the stock market and then attack accordingly to make their bets pay.
Take a look at the effect on global shipping the Houthis have had by getting lucky a few times in the Red Sea. Being a global pain in the a$$ and disrupting shipping is the Houthi goal. Their Red Sea success would pale in comparison to the deterrent effect of one hypersonic hit on the shipping route around the African continent. An additional single hit in the Straight of Hormuz would have most of the world crying uncle. They aren’t in this to sink a few ships, they want to destroy the shipping lanes with the terror of what they are capable of.