The short answer is because that's all they need to be...two feet underground, four and a half feet above. Over the years, the entire industry has moved from 8 feet to a 6 1/2 foot post standard because it found there was no advantage to taller or deeper-set posts. In fact, nothing was gained in strength for the extra digging labor and material costs of longer posts.

Please note that we can supply posts of any length from 4 feet to 10 feet to fit your needs.