Countries like Iran and China, provoke US ships but in ways they know won't illicit an offensive response. They'll for example, play chicken and stray right into the obvious travel path of US ships and force US ships to change course to avoid potential collision, even if the Iranian vessel was going to move at the last moment anyways. And with the size/weight of ships, there is lag time between movements happening, so a miscalculation on either ships part, can result in an unintended collision.

But the problem with this tactic is that it also allows Iranian vessels to herd US ships in the direction they want, which could be used in a surprise attack or diversion, so it's just bad policy. As long as they know we'll move, they can plan attacks around it.

And Iranian ships regularly do this to vessels in the region. If a collision were to happen and a US ship were to be damaged or sink, it would be very costly for us, while Iran might lose a cheap boat. Then you have to salvage and hope information/hardware from the ship doesn't fall into enemy hands, you have to keep a large presence there to guard the damaged ship, etc. Very costly.

Given Iran's behavior, it's time things have changed.