Regardless of the outcome, we will still need to train with and use these weapons so long as adversaries are willing to do so. Otherwise we will simply lose.
Unless new tech like drones obviate them, analogous to how guns made armor obsolete.
Absolutely the armed forces need to train with and use these. The intent of the study is (presumably) to figure out how to train more safely by understanding the impact, choosing smart limits, and educating leaders and medics as to the symptoms to look out for.
For certain values of "we". For nuclear-armed states the threat of invasion is 0 and there's no danger of losing anything more substantial than face and whatever they've invested in foreign adventures.
Israel is nuclear-armed. They seem pretty concerned about invasion. Nukes are a very large hammer and your toe might be too close for comfort.
The US is more expeditionary, anyway. So long as Mexico is kept weak and Canada friendly, invasion isn't a worry. But we have allies and friends all over the place.
Unless new tech like drones obviate them, analogous to how guns made armor obsolete.