What I like about it is that when users hover over the image, they can see some basic information about your channel (name of the channel and number of subscribers) and when they click on the image they are redirected to your channel. This is especially useful for videos embedded on other websites. It allows people to be redirected to your channel and subscribe if they enjoyed the video, even if they are not on YouTube to begin with.
This annotation acts simply as an added function for videos without a title built into the production of the video. Users can customize the color, font and size of the title box they wish to have for their entire video or if they wish to, they can cut their video in various sections with various subtitles. This annotation is more helpful for branding purposes because it helps clarify for the user what the video is and what company is being represented.
Lastly, Google has recently changed the way they present video in search results. Previously, video results were lumped alongside all results. Now, Google is employing a new video carousel which presents the top video results separate and apart from the rest. There are an average number of 8.5 videos on the carousel, meaning if you can get your videos highlighted here, your chances of attracting views are significantly higher. It’s not like an amusement park, there is only one ride, and it’s vital your video is on it.