We call those unproductive branches suckers as well. When people corrective prune their fruit trees in this area they inadvertently cause suckering. We know that leads to more pruning which leads to more suckering and you and I both know that circle never ends with fruit rather unproductive growth. There is always some suckering that occurs naturally. This concept is why I tip when the plant is young so that the lateral growth occurs early and the suckering later in minimal. I tip prune my trees later to keep them vigorous and productive but avoid needing to take off enough to cause suckering. I do like to keep my trees a little taller than many people do so that I get more fruit in less space.