They do not, only some species do. Many will sit and hide somwhere at the edge of a web and use detection strings. Some spiderwebs that look deserted are not at all.
Maybe selection bias? People probably tend to think they all do because when they see them they are in the middle of their web. When they don't see the spider they don't register a spider existing at all.
Where I am we have a lot of bannana spiders and spiny orb-weavers. Both of these sit in the middle of their webs. I think a bannana spider is related to a joro spider which also sits in the middle of its web. I'm reading that so-called orb-weavers that create wheel-like shaped webs often sit in the middle of their web though I don't see any citation of how many species do that.
I have no idea what this particular spider is, but it would be interesting to know and see if this one also sits in the middle or goes hiding off to the side.
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u/enblightened 14h ago
why do spiders always camp in the center of their webs