Arguably, the purpose of a search engine is to help people find sources that they don't already know about. Ideally, Google Search should present a diversity of results (the long-term trend of declining search quality, notwithstanding).

Google News, however, isn't a search engine, it's a link aggregator curated by a multi-armed bandit that seeks to maximize clicks and minimize political blowback (i.e. via censorship). Providing a diverse set of news sources is inconsistent with these constraints.

If it wasn't obvious, Google uses Search to identify topics that reach a large enough audience, and then they build specific properties around those topics curated by algorithms in order to create screen space in which to sell behavior modification products* (ads). While Google News, Maps, and Local are the obvious ones, even AMP fits this model with an attempt to monetize the "waste heat" of the lower click sites by appropriating their content.

* gfodor's observation that ads are behavior modification products: https://news.ycombinator.com/item?id=19798178