Why does the internet "need" this? Anonymity and pseudonymity are features, not bugs of the internet. Eliminating them will supercharge surveillance and government/corporate control.
The short answer is a lot of potentially useful decentralized protocols completely buckle under the weight of Sybil attacks, so if Sybil attacks were impossible, there is a whole lot more that could be built
I don't believe that they do, in fact, it is probably trivial to make a fake WorldCoin identity, but people who support WorldCoin largely support it on the assumption that this is not possible.
I think the people who support Worldcoin do so either on the basis of it being another shitcoin they can make money speculating with, or because they're in Sam's personality cult.
This is why it's frustrating to discuss WC. WC preserves anonymity and pseudonymity entirely. People assume it doesn't and then it perpetuates the misinformation around it that make people hate it.