With wikipedia or projects like Open Street Maps, vandalism, spam, and poor data quality are problems at scale. In particular, crowdsourcing does not work for curating commercial data or information where you can profit by spreading misinformation.

For example, in the cryptocurrency space. Projects raise funding through initial coin offers (ICOs). In an ICO, you can contribute ETH to a smart contract for the promise of tokens in the future. Having an openly editable list of ICOs and their contribution address would not work. The list would be quickly spammed because malicious actors have a really high incentive to put their personal wallet address as the contribution address.