IIRC youtube enables maximum monetization on videos that are at least 10 minutes long. So you end up with a mixed bag of 10-minute videos where some are content that could've been said in a couple of sentences and been 30 seconds, that were stretched out into 10 minutes of filler, and some where the content should've been 30 minutes or more, squished down to just over 10 minutes to try not to have an intimidating video length.