Those you mentioned are hardly happy endings, more like bittersweet ones. They fall in-between and they don't please anybody, your average "oh well, at least" endings. Those are erotic books, if the content is not good for you who cares how it does end.
(Like you mentioned) "When you let go of my hand": guy beats bad guy and is rewarded with the cumdumpster that maybe is pregnant
"Hanahira Itazura Seitokaichou": evil old man is also beaten and probably jailed, guy gets a cumdumpster anal doll back.
"Koukai Benjo": guy gets girl back after he's (yeah, he) mindbroken into a femdom anal doll and girl has been literally fucked by the entire school
"Aaan Megami Sama": guy gets a harem after all the goddess in said harem were fucked by pigs, shotas, hobos and so on.
"Saint Foire Festival 1": girl is raped out of her first time because of her mother pimping her to cover the debts, the day before her father's return could save her. She ends up killing her mother and confessing her love to her fiancee. Hints of her being preggo by rape.
"Summer Netorare": it turns out it's a dream. It's still a dream about cuckolding so it's not like it makes difference.
and there's plenty more
Summer Escalation fits in said endings because the "good" part happens when the work is over (it's actually pretty much a classic "cuckold" work, he's stimulated into fucking her after seeing her taken like a bitch, same for Tsuma Sacrifice with the difference that he's turned into a cuckold but at least he gets a share of the "pimping" pie). Your Wife's Secret (not True) Face has also a cuckold end, he gets some but she's his wife and he can't do anything but share her. The lolicon one is not netorare, it's a story about a very unlucky little girl he happens to save.
It would be like giving a happy ending to the Midgard series...who cares? There are over 10 books worth of cuckolding, let all goddess fall victim of the darkness and give proper closure. To use a "silly" comparison: you don't make a bucket of piss clean by pouring water into it. It's like those stories when girl is deflowered, fucked silly but at the end you get her back and she gives you her shithole virginity, rather than erotic it feels like a slap in the face.