Earlier quoted context omitted.
Because knowingly helping people commit crimes generally counts the same as committing the crime yourself. I.e. federally in the U.S. under 18 USC 2a https://www.law.cornell.edu/uscode/text/18/2 The software you're running being "simple" isn't a defence for doing illegal things with it - like aiding others commit crimes. There are a few internet/copyright safe harbor provisions (in the US) that might maybe (probably…
Wouldn't particular knowledge be required? I'm sure Google devs know in the abstract that Google search is used by criminals to help them in committing crimes, but that clearly is not illegal in and of itself.
It's kind of like Kim Dotcom's defence of his systems where he was saying that he was making attempts to remove content from his systems in compliance with DCMA requests. That is, the claim is his systems were legal because even though people were using them for illegitimate purposes, he was actively working to prevent that from happening.