It's sometimes war, sometimes poverty, sometimes government persucution, sometimes other things, sometimes a combination.
You have this rosey view that anyone can be successful if they work for it, but you don't seem to be able to comprehend that some people aren't simply born into luck like you were.
No one, puts their kids in a boat if they don't need to. You wouldn't go somewhere else you would be likely to live in poverty, especially given you are going to start again with nothing.