Because it is free and unbiased and will in time return to true peer review (which is not peer review at all but rather ... senior review).
What I mean by senior review is that the present notables will comment on new ideas, drawing them to the attention of a wider audience. It is a mechanism for moving up the hierarchy by judgement of superiors.
Whoa! Wait a minute! That's gonna' kill the golden goose ...
Let me describe the Actual Situation.
This is already beginning to happen. Notable scientists are moving to the Web to publish their work which is deemed unpublishable in a standard review such as the Physical Review. Any work might be deemed unpublishable for any reason. That it is "no good" isn't even one of the main reasons. Often a paper is eliminated from consideration because of its source or ... its content may run against the political grain. Right ... politics again ... even here.
But on the web ... this will happen.
The notable scientist-teacher will be confronted by his students with the findings of their web searches (for new ideas). He will be forced (socially and academically) to comment on them ... for or against ... it doesn't matter. In return, his students will judge his judgement.
Or, take the case of say ... Richard Feynman. Were he alive today (and alert), he would be all over the web looking at all kinds of "stuff". It's what he did and what got him the respect and admiration of a generation of students. He was "approachable" on a wide variety of subjects and was not afraid to "get his hands dirty". In other words, he valued the honest search for the truth above his scientifc reputation.
This is the type of "notable scientist" who would go to the web without being pushed into it. Now, what would happen to some obscure scientist's ideas (expounded on an obscure web site) if those ideas were reviewed on Mr. Feynman's page? Right ... Mr. Obscurity would get an enormous number of hits (ala Einstein-Kaluza) ... and if the review were favorable ... that Mr. Obscure gets his 15 minutes of fame whether anyone thinks he deserves it or not.
Eventually, we will see free "Review Sites" supported by major players who publish their own works as well as commentary on things of interest published elsewhere on the Web. Once the major players move to the Web ... the present review system will become part of the history of science rather than a guiding force in science which it most certainly does not deserve to be.
I expect then to see a wide variety of ideas to be discussed and reviewed and commented on which more closely resembles a Gaussian (fair) distribution of ideas rather than the queer distribution schemes now prevalent (shown below).
And scientists pay big money for the Physical Review and get 90% gibberish in return. Web = free and as good as you can make through furious competition. Why on Earth would anyone wish to confine themselves to print? To hide. To hide the fact that they have no new ideas and are living off the glow of past successes centuries old.
Why Feynman didn't want the Nobel Prize
Richard Feynman had a "gut" feeling about the Nobel Prize but couldn't express it in words ... so he accepted it.
What he felt is this.
When you accept an award of this nature, you confer upon the judges the Mantle of Authority. Such judges have not earned this distinction by objective achievement. By accepting an award you are, in effect saying, that you are serf to their feudal lordship. If they had put a gun to your head to get this, you might have refused. But if they give you a few hundred thousand dollars and "praise" ... you accept serfdom and bow (literally) to your masters?
Awards of this type ought to be abolished for ... achievement seems to be inversely proportional to the giving of them. What is this ... Hollywood? Does everyone need to be stroked?
You can see why I think little of Galileo for bending to the will of the Church. Scientists have been kowtowing to those in authority ever since. For them, a much better moral-philosophical example would be Archimedes.