Why should i take the freedom of making proprietary forks away from people?

My goal with open sourcing my software are to make the (software) world just a little better, i do that by writing the best software i can and hope that as many people possible use it, if i write the best ftp library in the world and you need a ftp library for your proprietary program i hope you use mine instead of an inferior implementation.

In my world view i do not loss anything by you making a proprietary forks of my work (i still have my version of my work with my license) but you and your users are getting a better product.