Well, because it means that other energy generation sources like oil, gas, and coal aren't being used there instead. Since they cause far, far more harm than nuclear waste does, it's a net win.

the waste isn't a win, of course, but is a downside of a tradeoff that is massively weighted to the upsides for society -- that is (otherwise) completely clean always-on high capacity energy production.

We understand very well how to safely handle nuclear waste and make it a very (very) low risk downside.