The stigma of nuclear weapons are primarily it's long term nuclear pollution and impact on non-combatants.
Destruction of strategic assets through cyber attacks, micro drone attacks and other similar methods won't trigger the same psychological reaction as a nuclear blast on a major city/industrial center even if results in the same destruction of strategic assets. The rally cry for war will have more fertile ground when people face the viceral experience of a radioactive heat wave.
Even as tactical weapons, use of nuclear warheads results in long lasting pollution that affect the neighborhood and potentially the globe. The use has high political costs, thus putting them very high on the escalation ladder.
Once 4th gen nuclear weapon/
becomes feasible the proliferation of tactical nukes will become more attractive. Usage will become a easier decision to make as it comes without the long term consequences of radioactive fallout. Usage of nuclear weapons on population centers will still carry the same political weight. Tactical nukes on military targets the other hand will be seen as a variation of the
or
but exponentially more destructive. These pure fusion warheads can be employed in devastating anti-ship, bunker buster, anti-infrastructure weapons.
If an entity wishes to absorb/conquer another entity, use of current polluting nukes lowers the value of the conqured land within the new system. While clean nukes won't have that issue. This will open pandora's box for nuclear proliferation not just in number of warheads but also how much lower on the escalation ladder it will be used.