That’s because cancer is an umbrella term that encompasses tons of diseases. It’s not one single gene mutation that causes all of them that you could just find and fix forever. Usually it requires many mutations for a cell to become cancerous, so curing cancer is basically like playing whack-a-mole.

Cancer is still your own body’s tissues, so often the hardest part of developing treatments is finding something that will kill the cancer without fucking up everything else. Like, sure, sodium hydroxide kills cancer but we’re not going to just start injecting it into people’s veins.