General theories are what happens when people who don't know any better decide they can crack what's going on with life, the Universe and everything, which they can't. Because if they could, the Universe would be replaced by something even weirder and more inexplicable. There are also theories that this has already happened.
The Universe and why nobody wants it to change Edit
You see, people like the Universe we live in currently, or at least everyone except those who don't and who were very offended when, in the beginning, the Universe was created. On Earth, people think that, as ape-descended lifeforms, they should never have come out of the trees but instead stayed they sulking. Some even think that they should never have come out of the sea. Many people agree that this is certainly true for Vogons, on whom evolution has entirely given up. Anyway as everyone worth listening to agrees that the Universe is a good place, they wouldn't want to have it disappear. Even those who think the Universe is a bad place don't want it to get even weirder.
The Universe and how everybody stops it from changing Edit
To prevent the Universe from changing, nobody ever tries to find out the truth and instead, they stick with making up fantasies called theories, which are all wrong. On Earth, people used to believe in something called a phlogiston which is an utterly stupid fantasy. Now they believe in electrons, which are also stupid fantasies. And as a cover up all the physicists make their fantasies incredibly complicated so nobody understands them at all. This means that the Meaning of Life, the Universe and Everything, or rather the question will hopefully never be found, so everyone will be happy. The Meaning may not be even be that calculated by Deep Thought but instead be God's Last Message to his Creation.