Why most embed feature doesn’t work?

WordPress relies on the open standard for embedding called OEmbed. This is what makes Youtube URLs turn into video players when copy pasted into a post, etc

By default WordPress only supports a predefined list of OEmbed providers, so it knows how to ask Youtube or Vimeo for an embed snippet, but 9gag isn’t in that list.

On further investigation, it doesn’t appear that 9gag has an oembed provider. I ran the 9gag URL through an OEmbed tester at https://oembed.frdnspnzr.de/ and it could not find any means of using OEmbed.

If 9gag did support OEmbed ( which it doesn’t ), it could be added via a plugin using the API calls, telling WP what a 9gag URL looks like and where to go for the snippet