As it has been pointed out by others, research data shows that plastic bottle caps are a significant part of trash that is washed onto beaches. In order to prevent that bottles now come with tethered caps. From this point of view this measurement might be understandable. But does one really lose the caps of these bottles that often? Is this really the problem?
Where I live these kind of bottles are part of a deposit system. When you return them at a supermarket you get your deposit (25 Cent) back. This alone ensures that these bottles barely end up anywhere in the enviroment in the first place. When these bottles are returned at the supermarket, all of the bottles do have their respective caps screwed on. This method is practical, as you can collect these bottles wtihout having to deal with leakages of excess liquids.
I never had any issues regarding that the cap is still attached to the bottle, which could be an issue when it comes to recycling these bottles. One major problem when it comes to recycling of plastics is that it is crucial that these plastics are separated by the material they are made of. That is why it is impossible to recycle compound materials, as they can’t be separated from each other (i.e. tetra pak, tetra bric). The most common way of getting rid of these kind of packings is to burn them and use their heat for generating electricity.
These plastic bottles on the other hand can be recycled easily, as they consist of only one material (PET) - given, that the label is made of the same kind of plastic like the bottle itself.
I don’t know if the bottle cap is made of the same material (PET) or if this is another kind of plastic (ABS, PS, …). Making these bottle caps from the same material as the bottle itself would impose a greater impact than tethering them onto the bottle.
At first glance this measurement sounds like a low-hanging-fruit-greenwashing-attempt that hurts nobody. Very similar to the ban of disposable plastic cutlery or the ban of plastic straws. Don’t get me wrong - I think that these things are an important step towards reducing pollution and garbage overall, but did you ever ask yourself: “How does the garbage get into the ocean in the first place?”