I don't agree with the previous answers.
Your question is very interesting and it's also the key to succed on YouTube.
So when you make a video try to engage a conversation with the viewer. Of course he will not answer but the key is to create a dialogue with him. There is a lot of tips for that so i recommand you to look at some popular youtubers and you will notice that they often speak to the viewer directly.
Moreover when you make a video you must aim a 80% or more watch time on it. To make that a good think is to ask a question to the viewer. For exemple you start your video by an interesting question ("do you know why ... ?") So the viewer will stay 30 more seonds to hear what you have to say about it. When you have finished try to focus his attention on another point and speak about it, etc.. In fact everytime you speak about something, instead of speaking directly about it you must convince the viewer that what's you are going to speak about for the next 30s is interesting. By making good transitions to keep the viewer you will succed to keep him for long minutes on the video.
I admit it's not easy at the begining, but start with a 3min long video and try to have a 80 or 90% watch time. If it doesn't works analyze your stats to see when most of them quit the video and what you could have made to keep them 30 more seconds.
I definitely think that it's the key to become a successful youtuber and sadly few people know it.
