I believe ball ammo is considered the most reliably feeding ammo, and perhaps this and it's general purpose nature are good reasons for it's common use in most military situations, where one is trained to be effective with same.
Self defense ammo, from HP, SP, to frangible and beyond is all good stuff, but impractical for various reasons in staged battle and other scenarios. Again, the mission should dictate the appropriate tools, and a willngness to be supple with mission planning is only smart. For me, at least I never plan on missing a lot, it happens with suffiecient frequency on my part without any planning!
SatCong