Maybe they do that to maintain visibility and/or integrity of their goggles from the elements like sandstorms and rain? Plus, other countries do it, so why not?
The whole point of military grade ballistic goggles is that they should be multi-coated to prevent things like fogging and rain/spray build up that would obscure vision.
If there are such basic quality issues, it would be infinitely better for that to come up during training than to only be discovered in combat.
On the pictures provided, note that while those soldiers also have their goggles hooded, they are still wearing ballistic glasses.
The goggles should be airtight once properly secured, and are intended to protect the wearer from things like smoke and gas as well as kinetic impact. As such they can get pretty uncomfortable pretty quickly in even mild climates, so it’s no wonder western troops deployed to the ME prefer lighter weight glasses which allows air to freely flow for better cooling.
Those PLA marines should either be wearing the goggles they were issued, or they should also have lightweight glasses issued.
But I think By78 has a point on the PLA still having a mindset of trying to protect kit rather than use it.