Sometimes the smaller secondary ears do mature and are worth harvesting and sometimes they don't. It just depends on how well the secondary ears pollinated and on how vigorous the corn plants remain, and it even depends on the variety of sweet corn you're growing. The varieties I grow generally produce two good ears per plant, and sometimes even a third small ear lower down on the plants some years.

Are you saying you're only getting one big ear per plant and then have a smaller second ear?

I am growing 'Incredible' which does have two to three ears each, but the second ear is smaller. I am growing 8 in a part and 12 inches between rows due to limited space

Oh, well that sort of close planting may prevent the seond or third ear from developing. They are more likely to develop better if the plants have wider spacing.