In all seriousness, if you've already put in the effort to write a book, it's pretty hard to lose money selling it through a print-on-demand service. (It might be hard to make money, but it's pretty damn hard to lose money.)
There is more to life than money. Writing such a book allows me to share my wealth of knowledge. So what if I don't make a million dollars out of it? That's not the purpose. I want others to benefit so they can grow their businesses. And in turn create new opportunities for others.