Seems like you dont recognize its purpose, because like i just said, in the earlier stages it's meant to be backing up fighting units so someone can hold an attack off totally (ie not let grunts in their line at all with any luck, or if any get in there's defending grunts in the mix so peons arent getting attacked, and if any die to splash damage it's minimal). and in later stages, it's meant to prevent set-it-and-forget-it attacks, to keep the base from being flat wiped out without a full squad of ogres+dk. They might get the peons but as long as the ct & hall hold, you've retained that expansion on the map, and can start pumping new peons, even if you didnt have enough ogres to hold off the attack and werent able to get more ogres up there quickly etc