It doesn't just help them with sales. Sometimes, changing the name and other small details is the ONLY way that certain gams can be sold on platforms like steam. Also, H games aren't the only genre of games affected by this. A puzzle game named "Stealth Bastard" had to have it's name changed to "Stealth Inc." for it to be sold on PSN. It may seem unnecessary, but that's what it took for the game to be allowed to be sold on that platform. If that edit weren't in place, PSN would've rejected it and a lot of people would've never got to experience that masterpiece of a puzzle game. That same logic applies to companies like Kagura when they try to sell on platforms that raise their eyebrows at this type of content. I don't view those edits as handicapping the game, they're more like small tweaks that had to be done for the game to be released to a person's favorite - perhaps only - method of gaming.
However, not everyone sells the "edited" version. If you buy H from a place that specializes in H you'll get the uncut version