Know Your Meme says it started out as a joke poking fun at the idea that the sequel is going to be even worse than the original (already poor quality) material. Interesting but not really important to the rest of this post.
As I'm sure most people (Hang on while I check the counter. Wait what I broke over 100 views a couple days back? This is news) are probably aware Hollywood likes recycling material. To them it's a safe bet since there's a built in audience. Take Constantine. The movie had pretty much nothing except a few 'in name only' characters and a sort of kind of but not really resemblance to one of the plotlines and it would have probably been better received if it'd gone as it's own thing since it actually was a pretty good movie for what it was.
My last post didn't even begin to touch the surface. Apollo 13? Book came out before the movie. Forrest Gump? If anything the movie toned down the number of historic events Gump was in. Swamp Thing? Alan Moore comic. Lonesome Dove? Book. Anything with Uwe Bolle's name attached to it? You get the idea right?
Like i said a few paragraphs above Hollywood likes going for a 'safe' bet since in the end sure they might tell an entertaining story (for some value of entertainment) but at the end of the day it's a bunch of people wanting to make lots of money. To do that they could take an unknown script from an unknown screenwriter about an unknown property, or they could go with a known quantity on all of these and while they might and often alienate the 'true' fans (dear God don't get me started on the whole 'true fan' bullshit) they'll draw in enough people more often than not to make their money back and then some.
This does not make them an inherently evil industry, actions for the past ever since the MPAA's inception to one side. Everything is a derivative of a remake of a half-remembered thing. Take Avatar for instance. Dances with Wolves in space you say? Nope! John Carter of Mars, which itself is just a 'stranger in a strange land' story. You know what i'm talking about right? Person we find somewhat relateable gets dumped in fantastic and unrelateable situation and has to adapt which gives us a look at our own culture.