Alright, I've been thinking about this for a while now.
In my opinion, they're not necessary. I don't need to have sex with a girl to feel anything towards her. (There are people like that, though, and I'm not telling you you're wrong.) Lonely Yuri, for example. My favorite VN of all time. All-ages. I felt like I knew Seri and Fusa better than Nagisa and Tomoyo. (Tomoyo After is another problem I have, but... At least KEY gave us an all-ages version.)
Or, think of it this way. (I'm quoting a friend here, and if he reads this, I hope you don't mind.) "H-Scenes are like watching a good friend have sex." That'd be uncomfortable, no? I get that most people imagine themselves as the MC and all, but some don't. Hell, who would (I'm sorry for this, Tom. I'm not saying I dislike you or anything, but...) want to play a game that involves raping people, with either of those situations in mind? (Again, no offense to anyone who likes them.)
If you want to keep H-scenes in games, just play nukiges. Keep them out of my story VNs. At least give me an option to disable them.
I could go on and on, really. But I'll leave it at this.