My reasons for putting my written work on the web are similar to those of other writers pioneering this route and basically boil down to: Why not?
Besides, writers don't usually make a lot of money from being traditionally published anyway, so what have we got to lose?
Some other thoughts about offering Free e-fiction:
1) Let's hear it for the variant text: ie, if something is not working for your audience, you can change it. Yes, change it. If there is a mistake, it can be fixed. Don't you think the ancient storytellers got to improve their tales over the years? E-fiction gives us that freedom again.
2) Experiment. The first novel I will be putting up was written with a mind steeped in traditional views of story writing and publishing but, with e-fic there are new things to try. Stories told in short bursts of, say, 100 words, that people can catch up on during their lunch breaks, or in even shorter slugs like haiku or other poetry that can be read on mobiles while riding public transport, - or waiting for it.
3) Creative Freedom: The stories can be as long or as short as you wish to make them. They do not have to be 60,000 words, or 80,000 words, or 120,000 words or any other number. Nor do they have to be part of a "six-part trilogy" that will be expanded even further to twelve parts for marketing purposes.4) The story can demonstrate its worth before a publisher buys it. Publishers can see when a story is popular, thus taking some of the risk out of buying and publishing a story conventionally. Publishers and agents can also see what an author is capable of before they take them on. In this way, online and traditional publishing work together, which is great for people who love books, and for people who just love stories in any format.
More reasons will be added as I think of them.
In the mean time - happy reading!