There are several reasons why the military don't use it.
The first reason is that hollow bullets often can't pierce through hard objects. Like car doors, some vests with equipment etc.
The second reason is that if it does not kill, the suffer from surviving could be greater than with an bullet that went just through (all weapon that hurts, but does not kill, are today forbidden in the military)
The third reason is that when an enemy take hostage, so can't you some times shoot through the hostage with an hollow bullet, while the standard 5.56 NATO till pierce right trough. This is why police use hollow bullets (will try not to hurt any others than the enemy), and why the military don't (were it is important to kill, despite outcome).
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