Because after 100 years, technology will have advanced to the point where we can safely and cheaply extract the thousands of tons of still-usable fuel from it to generate quadrillions more kilowatt-hours of electricity, and the leftovers will only be dangerous for a few hundred more years, and so shipping it to the sun would be a waste.
Did you know that there's more potential nuclear energy in coal ASH than was produced by burning the coal?
I didn’t say we should stop researching technology to re-use the spent fuel in the next 100 years. Of course we should do that.
But we do NOT have to store the current “waste” here forever. That was my point.
At some point what we can’t use, we can dump into the sun.