Video content, particularly on youtube, gets very little traction here generally.

I watch his videos, but not from links here and that is probably what you are seeing: those of us who might follow your link have already seen the video (likely via grayjay rather than youtube) and will skip over it to the next interesting new thing. People who don't already watch him will see “[video] (youtube.com), 1 point, discuss” and think “oh, another video that could be a few paragraphs of text which would be much faster to read than watch, that so far no one else has seen as worth interacting with, preceded by two unskippable adverts”.

A link to youtube is only going to get much attention if it is lucky to have a title that jumps out to a few people so it gains the first few votes and/or comments that get the ball rolling. Even then Louis' videos aren't going to get a hot debate going: most people either entirely agree so don't see the point commenting further, or they aren't the sort of people who are reading HN at all or are but don't follow video links.