I agree that most vlogs can be boring if they are on the everyday life of the person that is recording it. However, with that being said, if a vlogger can incorporate a powerful message in every vlog that is different every day then they become interesting for me. It then kind of turns into the equivalent of reading a column, but instead of reading the content you are watching it.
All in all, I think the reason that people watch videos (or do almost everything in life) is because they feel they somehow gain something from doing it (money, job security, a partner, a good feeling, you name it). If a video, like a quality text, has a message that resonates and sticks with people then that makes for an interesting video. It is just as possible for a vlog to get this job done as it is for any other video, in my opinion.