I can give you the reasons that brought me here.
Security, Privacy, Freedom, Usability. In that order.
Usablitiy shouldn't be the first concern when you are using a computer.
Because, windows is very convinient, it does a lot of things out of the box
that we like it to do.... But it has thousand of viruses, it has backdoors,
it's closed source so EVEN if they were to now stop mistreating their users,
we wouldn't know for sure, because we couldn't verify it by ourselves....
Java, Flash, Skype, whatever, there are many softwares that RUN on GNU/Linux,
they are developed to be used in GNU/Linux, but they are not respecting you
as a user. And let's be honest, it's wrong to write a software that has back
doors. Completely wrong. BUT, it is not wrong to write software and don't
give the source code away. It's your right as a creator to do as you wish.
Just don't expect people to trust you (or at least people who like to think
with their own brain, nowadays a lot of people don't do that, lol).
So... it's not WRONG to use proprietary software, it just PLAN STUPID.
What do you treasure the most, having your little baby's photos syncronised
in DropBox and Facebook so that all family and friends can see him, or making
sure that no one is taking those photos and using them for advertisement,
selling them to pedophiles, preparing a kidnap... ? Answer that question and
you will have your answer =)
This is my reason, I am not trying to convince you, I am only saying what
motivates ME!