Selling books is tricky. Most of the indie authors I speak to seem to find it almost impossible, struggling to sell even one book per day. If you are not already well-known, it's hard to persuade people to part with their money. It's a gamble for them but there's a way around that.
Over the past months I've also posted free samples in a variety of other places, including Goodreads, my Astronomicon blog and Wattpad. I've given up on Goodreads as I've made no headway at all with that, and my blog doesn't really get enough visitors to make any impact. The only place I've been able to successfully encourage people to take a look at my work is Wattpad.com, and I would not rate that as a great success. Like any popular social site, it's hard to stand out from the crowd and get that all-important word-of-mouth marketing going.
My most successful offering of free chapters has been Astronomicon: The Beginning on Wattpad. I've managed to get a few hundred reads there, but I'm still looking for that elusive means to turn it into tens or even hundreds of thousands.