Miles, apples are diploid, meaning they need two trees to pollinate the flowers, the resulting fruit is a combination of the two trees genetics so when you plant an apple seed the resulting tree's fruit will have some combination of the two "parent" trees characteristics. There are more than three thousand recognized varieties of apples , most of which were originally open pollinated in this way, all apple trees that produce true to type are grafted trees which use scion wood from a donor tree. The root stock used for grafts determines the mature size of the tree. While a tree grown from seed may produce crisp, juicy, sweet, wonderful apples it may also produce fruit which is mealy, mushy, with poor flavor or is prone to disease, and since it takes several years for a tree to produce a crop it just makes sense to grow grafted trees so you know what you will end up with. That said, if you have a lot of unused ground and a few years to wait, grow some trees from seed, you never know you might end up with a superior apple and if you don't you can always feed them to livestock or use the wood to smoke meat.
