A thousand children are born every day with HIV. There 2.5 million children with AIDS at the end of 2009. How easy was it for them to avoid it?
Your attitude isn't far wrong as a Western perspective, but the truth is AIDS is pretty rampant in other parts of the world (particularly Africa). Over there, culture & religion are huge roadblocks to stopping the spread, which means there is a great deal of 'collateral damage' to people who you'd think would be safe (children, spouses, etc.).
Whatever you think, 1.9 million people died in 2009 from AIDS, while 1.7 million died from tuberculosis. Not that tuberculosis isn't a fine target for money too, I just think its too facile to dismiss AIDS as 'easy to avoid' and therefore not worth pursuing.