Why do you think Bitcoins are free or should be free or that you should be able to get them for free? What on Earth every gave you this idea?
maybe i should sell stuffs and set as payment method "Bitcoins" only. it seems to be the only way to have bitcoins for free.
This is not getting Bitcoins for free. It is a trade of something of value for Bitcoins. Not free. Maybe you don't know what "free" means or maybe I don't understand what you mean by "free".