Why is life so unfair?

I just don't get it why is life so unfair to some people?While some others live happily and get married,find love and have someone by their side there are some people who struggle to survive every day by themselves,fighting illnesses all alone either physical or emotional ones...no I don't wish for happy people not to have fun I just wish that all people would have their fair amount of happiness in their life...But as every day passes by I realize that life is indeed unfair to some people and for the believers of karma well there are some people who suffer even if they haven't hurt anyone before...so karma doesn't really exist after all..