It seems that you've played only typical VNs at the moment. KS is incomplete so nothing can really be said about it... The Sagara Family was full of laughs, but still a simple love story. YMK is better than the other two in my opinion because it took it a step further by addressing and attacking issues such as bullying and drug abuse in high school students, but in the end it is still just a mostly normal love story.
Based on this, what I think you're feeling is that standard love stories just don't seem complete without the characters having sex. In this regard then I do agree with you, however
this does not apply to all VNs. The H-scenes are there to enhance the story, not to complete or make up the story (except in something like
Fate/Stay Night where it had plot purpose), so whether or not the VN has H-scenes is entirely situation and dependent on the plot, setting and genre of the VN.
Cause face it, you've only played 1 non-H VN (based on the info in your post), so making a claim like yours is bit pretentious. Try different genres of non-H games and I bet your opinion will change. I highly recommend
Chaos;Head,
Ever17 and
Clannad, all of which are non-H but still amazing.