I'm teaching a basic gardening class this fall. One of the questions I asked on a take-home quiz is:
List three important goals in pruning a deciduous fruit tree.
There are more than three good goals to aim for when you are pruning a fruit tree, but the one that has turned up on every paper so far is: Don't prune the lower limbs or you won't be able to reach the fruit.
It makes me happy to read this answer. I think of the fruit trees I've seen with lower limbs removed. There is the fruit, 10 feet up where no one can reach it. Useless. I am cheery when I think that these students won't do that.
Of course the other part of keeping fruit within reach is to train the tree when it is young so that it has a low first crotch. This is done by encouraging low branches when the tree is very young. If what you bought was a single, unbranched stem, you want to cut it just above a bud that is two or three feet above the ground. If it already has some branches, save the ones that are wide-angled from the central stem and well-spaced around the tree and from each other, remove the others, shorten the ones you have left to a few inches long.
The bottom line is that deciduous fruit trees, like apple, plum, pear, and apricot need training and shaping when they are young, or they won't be good, fruitful, easy to harvest trees. When you buy a young deciduous fruit tree, also buy a book with guidance on training and pruning it, with some nice line drawings to show you what to do, and you will be rewarded with more fruit and a stronger tree.
When I was a child we had a yard with 4 apple trees. In summer I spent a lot of time climbing into those trees, usually with a book. I always wondered why apple trees, in particular, were so easy to climb. Now I know. It's that low first crotch. Not only are the first branches within reach, but the low first crotch let's one climb up to get the rest of the fruit. Or read a book.