My understanding of stellar formation was that stars tended to form in clusters. The Pleiades open cluster is less than 100 million years old and the Hyades open cluster is about 625 million years old, and both still contain a lot of stars within a volume of a few cubic lightyears.
Now I look at Betelgeuse, which is only about 10 million years old, and I can't find any mention of any cluster around it. Same goes for Antares, another supergiant that is probably about the same age as Betelgeuse.
So, are we just not able to see the cluster of stars that these supergiants are part of (which seem unlikely to me) or do really massive stars simply not form in clusters but rather form on their own? Or is there some other process going on that's very rapidly cleaning out the clusters in which they formed?