there is another reason why these values are chosen - ppqs are chosen to reflect a true division of musical notes. Thus 96, 192, 384 etc are the true perfect ppq values, others are not.

120 is not perfect because a dotted 32nd note does not trigger perfectly between ticks.

96 ppq resolves 128th note triplets and runs out of resolution at 256th notes, maybe this puts it in perspective!