These USB miners are too old, there are better ones now with more Terahash mining power, I think people are still doing this hoping to hit the lottery one day, and so far few people have been lucky since 2020, since these USB miners are not taking so much power to run I think it won't hurt plugging in your wall and let them run.
It could be true that people might still be using those 333 MH/s miners as a "lottery" style mining. Even though it doesn't make any sense, i.e. you could use much more efficient but still cheap miners that are not as obsolete as those ones, but if you happen to already have one (or more) of them, just plugging it in once in a while just for fun, i.e. while you're working on your pc/laptop, won't cause any harm.
I don't think anyone would buy them just for that purpose though. If there are any buyers willing to pay the price as shown in the first posts, they definitely buy them for their collectible/sentimental value, not to actually mine with them.
I fixed the broken image in the first post.