Efficiency
What would it look like if he stacked three sonic bullets on top of each other in constructive superposition, creating an attack that could be thrice as powerful as what he would normally be able to dish out in a single impact?
Of course, he could also release those three same bullets normally in a barrage, but singular impacts were often more desirable than barrages. This was because damage was not necessarily linearly related to power.
That meant that three equal attacks did not cause an equal amount of damage as one attack thrice as powerful as one of those three attacks. There were many exceptions, such as piercing attacks and other means of inflicting damage.
But by and large, the damage rate of barrages of smaller attacks was lesser than that of one large blunt force attack.