Accidents happen and considering the amount of waste there would be have to be quite a few launches.

I'm not sure if there is a good list out there, but just some examples from memory: just last month space x failed to deliver satellites in the right orbit and I think one of the other incidents at the end relates to this one that actually exploded.

The second one ofc is a bit older, but still what is an acceptable risk to take when handling radioactive material? And the recent one also wouldn't be fun.

I would also imagine that handling the waste on the ground would make everything much more difficult until the launch.