Search engines do not intentionally suppress new and better sites/content (to the best of our knowledge) but it is the inevitable result of the algorithms currently used to calculate search result rankings.
Sites which have existed for a long period of time and/or have a large number of incoming high quality links have a significant edge over newer sites - even when these newer sites are providing noticeably better content.
This discourages many who create content on the web as months and even years pass without their work receiving significant attention. Sites are often abandoned long before they appear highly in the search results and thus high quality content is lost to the world. More importantly, high quality creators stop creating. Thus we lose not only the content they have created but what they might have created in the future.
On the other hand, sometimes older content of higher quality or better authority is buried under newer content due to algorithmic ranking. For example, a newer (but lower quality article) from a popular source might outrank a higher quality but less buzzy source. This discourages long-term maintenance of web content and oftentimes the content disappears completely.