When I first started playing, I most definitely had no interest in the h-scenes. However, it's been interesting - if disturbing - to explore where my sexual tastes lie in the years since. As for whether they are necessary... sex sells. Who would play a moege without h-scenes? Seriously. Well, some I would but I certainly wouldn't bother with most. As for sex in other types of eroge (excluding those where the ero is the point of the game), the h-scenes are often simply part of the story (with the exception of ones put in there just to be titillating, like school, bdsm, and public place h-scenes). As an example, the h-scenes in Kei's path in Dies Irae are very much a part of the story and serve as a point of hilarity and odd tenderness in the otherwise grim story. Similarly, the h-scenes in Jingai Makyou usually serve a specific point other than being still-frame hentai. I won't go into details, though...
However, in many games, the h-scenes do seem unnatural in how they are placed, and there is an excessive amount of emphasis put on the sexual aspect of the game. Moege are most frequently of this type, pandering to a certain crowd that likes to see girls of certain types in various positions...
