Because I don't. I never quite get people who expected to get a product they would love equally as much and especially that would cause the same feelings in them while watching as the original films.
That being said, similar to the comparison between SW 4-6 and 1-3, I can say the following about LOTR vs The Hobbit:
The older stuff had more heart. Maybe that's nostalgia talking, though.
Then there's the topic of special effects and while I am no enemy of CGI in general, it sometimes doesn't help. That particularly goes for the new Hobbit film and that CGI character I mentioned as well as a few more scenes where I thought: umm, that felt much more real in the films that are actually more than ten years older than this. I am pretty sure Abrahms' new SW film which supposedly relies a lot more on practical effects than the prequel trilogy will show why that's a great decision.

In the end, the reason I like the new trilogies but LOVE the original three films of both series is that the old stuff emotionally just stuck with me much more.

Yep. There are scenes that are probably nowhere to be found in Tolkien's works and have been added simply to have certain actors from LOTR reappear and some of those actually work. Others don't and I am pretty convinced two Hobbit films without an Elvish-Dwarven love story would have worked just fine.

Exactly, see above. Sometimes it just feels lazy. In the 80s you had to film a real raven fly out of a castle. Now you create a CGI raven. It's just not always the right thing to do.

Yeah a while ago already. They probably felt that this new title summed up the film much better and sounded more attractive. They're right.