In addition to the obvious use of responding to questions based on the material, perhaps it could be a tool for finding e.g. if and how a cited source relates to the article where it was cited. Abuse detection could also be one application.

I couldn't exactly find out what the goal of Wikipedia is from https://en.wikipedia.org/wiki/Wikipedia but it doesn't seem a "better search" would be opposite to those goals.

The paper also tells them how to solve that issue, which is what google would prefer. But they are letting wikipedia make that choice.