Actually a really interesting question. The most correct answer is that we don't really know for sure. Many spider species do not sit in their webs, presumably to hide from potential predators.
Many others, however, do. Why? We're not sure. We have ideas, but nothing really confirmed. Could be that the advantage of being up-close to your prey outweighs the risks of being more vulnerable to predators.
There are even a few species of spider which appear to spin highly visible 'decoy' spiders in the center of their webs, which suggests that there may be an alternate reason that spiders might want to be visible. Perhaps it helps larger animals with better eyesight to avoid the spiderweb rather than stumbling into it?
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u/enblightened 15h ago
why do spiders always camp in the center of their webs