Why hasn't research discovered a cure for cancer?

Aids came along and a cure was discovered almost instantly, compared to cancer. So, what’s the holdup with cancer? Surely, after all these years and billions of dollars spent, researchers should have come up with a cure by now. Is it all about the money? Is it about researchers and labratories adding to the unemployment rolls, if a cure is discovered? I do not understand why a cure is taking so long. Question: After billions of dollars have been spent searching for a cure for cancer, how come no end is in sight for a cure? Is it really all about losing funding and jobs?