RubberNinja's explanation of how the YouTube algorithm works really explained why.
The thing is, YT doesn't reward based on quality, per se. They reward based on view time and retention. If you release one amazing video per month, even if a million people view every video you make, that's only going to be seen as half as "valuable" as if you released 4 a month and 500,000 people watched them. And even that's assuming you make something of the same length.
If you carefully craft a 10 minute animation (which can take months), there's just no way to match someone who bangs out 15 minutes vlogs daily. Just go by math. Let's say you can churn out a solid ten minute animation on the first of every month. If a million people watch your ten minutes, that's ten million minutes. If 30,000 people watch my 15 minute LP's every day, that's 13.5 million minutes. My "product" is more valuable to YouTube.
YT seriously rewards fast content. It's not a good place to put high production products that take a long time. Hell that's probably why EgoRaptor went from animations to turning Game Grumps into his full time gig.
Keep in mind, I'm saying this AS a Lets Player, and one that puts a lot of love and craft into what I do, but I recognize that what I do is far, far more in line with YT's promotional style than content with longer production cycles. FFS while I was sitting here I finished editing four videos and they're uploading right now.