I could write something long and at risk of being classified, so I won't. I'll just say that all those low yield nukes exist because of the idea of proportional response.

Massive use of the big ones would result in a pyrrhic victory at best. Someday, someone is going to gamble that limited use will will not go there and response will be proportional and limited.

Very dangerous for the reason you gave. But when clowns are kings the palace becomes a circus. Disheartening indeed.