[marcus_holmes]

Because the point of the war was part of the plan to reform the Soviet Union under Russia/Putin.

The idea was to spend a few days, a couple weeks at most, taking Kyiv and the major cities, and then absorb Ukraine into a greater Russian state.

If they have to nuke Ukraine to make them do that, then that's not going to work. Absorbing a radioactive hellhole, with all the problems that will bring, isn't the plan.

Of course, the plan has gone badly wrong, and pretty much everything has gone the opposite to the way Putin wanted it do, so he could still nuke Ukraine just out of petty spite.