Good article! Google always seems to change their SEO algorithms as to determine who they will show structured data (rich snippets) for on their search results page.
Sometimes you can be #1 and they still won't show structured data, or snippets unless you come up with new, relevant, and non-repetitive content.
Also, have a healthy amount of traffic, and engagement with that traffic before their algorithm decides to show structured data the best way they think suits the user.
For more info please see the following Google articles:
https://developers.google.com/search/docs/guides/sd-policies
https://support.google.com/webmasters/answer/35769#quality_guidelines
Yes they often don't show them but they are still noticed. They tend to show up for content in certain categories more often.