It's easy to get drowned out in the noise of a larger videos comments sections and I can see why people don't bother.
What I have started to do is change my subscription settings to notify me immediately when there's new content from the larger channels. That way, I can get my comment in early and it will have less competition. Of course, the comment needs to be relevant as a minimum.
A recent example: I managed to get an early comment in recently that was half funny and very relevant to the video. Within minutes I had 15 likes and I noticed a small flurry of traffic to my channel, followed by a subscriber or two. It's worth noting that you should only do this for content that you actually like and have something to add to, but that probably goes without saying.