@icarushector
Well you asked for it. There's more reasons to read something other than liking it and those are my two big ones. Others, some of which don't apply to me are:
1) Because your friends are reading it.
2) Enjoying hating on stuff.
3) Completionist, trying to read as much as possible.
4) Paid to do so / you write reviews; think youtube personalities or well known review writers.
5) Fuck you factor, some people like to brag about the amount of what they've read
6) To expand their horizons, more experience / stuff read is never a bad thing and can help you as a reader <- This is pretty much the only one on this list applies to me
There are so many more, but there are the other ones off the top of my head.
As for more explanation to my big two, I want to know how something ends, regardless of how stupid or shit it is. I hate not knowing the answer to a question that's in my head, whether that be how an untranslated manga ends, or what the solution to a puzzle is and so on. I don't like not finishing projects either. The most that I'll do is put them on the shelf to finish later, but if it's something like a manga that only requires a chapter read each time there is an upload, I see no reason not to read that chapter. Nor do I see a reason to drop a manga solely because I dislike it and have already invested time into it. It's not unlike a sunken cost fallacy or hoarder mentality in some ways. Plus, there is a great deal of euphoria, a sense of accomplishment, when finishing a manga, especially when I don't particularly like it.
And since I hate seeing people complain about reviews or ratings on series that the reviewer has not completely finished, I finish it so I can inevitably tell said person to fuck off, because as you can see from the guy above, such people will latch onto any justification they can to dismiss an opinion they don't like. I guarantee you if I wrote a negative review of a series on MAL or something, with only 50/60 chapters finished, some moron would bitch up a storm. That said, I also don't like reviews or ratings on a series that has like 2 chapters or 4 episodes out, but there is a bit of a difference and is not entirely relevant. Anyways, I also don't like to completely abandon the possibility of change. There are some series that change drastically through out their life span that can greatly affect your perception about them. Is that at all common or enough of a reason to finish every series / dismiss the opinions of people who haven't finished a series? Not really, but it is one that I take into account. The more common reason is just to have as much information as possible and to confirm what I expected. Just like how scientists will confirm some pretty obvious shit because of the scientific method.
@wilddeath
IIRC, all people who can use the ring are descended from him. As for B, that's a pretty lame justification don't you think? That's like Fairy Tale "power of friendship" kind of shit. "The ring doesn't hurt him because he's nice". Granted, they could add some crap like the ring being sentient or housing the soul or Solomon or that Solomon put on some spell on it only to allow the pure of heart, but to me that kind of thing seems lazy and generic. It all boils down to the MC being special because he's nice, a rather typical insert fantasy for harems. "Being nice will reward you with tons of women". That said, what really matters is how they portray it, the execution. A beautiful song kind of sucks when the person can't sing and an awful song is amazing when the person is an amazing singer. So maybe what you've said is the case, and maybe they'll convey it in a convincing manner, but simply as a concept, and considering everything that's happened thus far, I don't accept that as an explanation. It's a bad song that probably won't be sung well.