Some people are so desperate to be accepted on YouTube and have four figure view counts that they'll nick a popular video from another channel and hope it pulls people in just so they can watch the view count shoot through the roof. Quite what these people think they're going to achieve I have no idea, but its obviously quicker than going out filming, making and editing something unique.
Other people just nick things regardless, butcher them and then claim their botching is real. "15 minute music interval man" is the classic example here. But less said about that the better.
People on YouTube these days care about quantity over quality.
There are certain YouTube individuals and channels who practice the quality over quantity and this is why they only upload, say, weekly or on occasion, but when they do, it's a good quality upload and it was worth waiting for.
So Tom Scott for example. This video, according to the follow-up post on the Matt & Tom channel, took weeks to edit apparently, but it was worth it and served to preserve a segment of how presentation looked on Sky and BBC News at the time:
But it only has 686k views. And yet this video below also from Tom Scott's channel, basically boils down to waiting for toast to pop up and it racked up 5.3m views and counting:
There is no accounting for what becomes popular on YouTube sometimes.
Josh and BBI45 gave kudos