What I strongly disagree with: People should not care about a manga when the author doesn't seem to care anymore. For one point, saying a mangaka doesn't care anymore after going through several hiatuses is just wrong. Take minor examples like Kaitani (Liar Game) or Inoue (Vagabond). Would you say both don't care anymore because they've went on multiple hiatuses? Heck, Inoue even stopped serializing Vagabond for almost two years because he was "out of ideas" or something of the like, yet he picked the series up again. Obviously both won't be confronted with the criticism of being lazy as they had/have another series on their hands, but one could always argue that they don't/didn't care about the other series anymore. Bullshit in my opinion.
The prime examples probably are Miura (Berserk) and Togashi. Both have a strong standing, neither could be forced by the respective companies to continue their work. If they don't give a fuck for their series anymore, they could always end it abruptly. They have both the money and the fame, there's no reason to continue the series when they don't care about it. And yet they continue without being forced to. It's not like the story is complete bullshit either, both still have the qualities they're famous for. How could an author, who is just forcing himself to continue, come up with a good story? When you completely loose motivation, usually (near to) nothing good comes out of it.
I see it more as a part of wanting to enjoy their life's. It's not like they don't care anymore, other things are just more important. Now fans or non-fans can bitch about it all they want but it's only natural that you want to enjoy your life to it's fullest. There's a limit to what one wants to sacrifice for others. Like I said, that doesn't mean they don't care shit about fans or their series, just that at this point they see other things as more important.
Now the other point: You don't understand why people care about a series when the author doesn't seem to care about it anymore - how am I supposed to not care about a series I like/love? You can't just stop caring about a series you hold dear for a long, long time, even when it looks like the author doesn't care anymore (which I think, is a pretty unreasonable statement to make anyway). We barely know about their everyday life, yet we're so fast to make a judgement based on our own opinion or rumors. I wouldn't dare to say why an author ended a series or put it on a long hiatus as long as I don't hear a clear statement from his side or know him personally. I can assume things but that's it, so people should stop saying things like they're the authors best friend.