A BST in the way that is being implemented for this Sprint is a bit too simple to see any real-world use-cases. There are many (more complex) variants of BSTs that do see production use. One very notable variant is the B-tree, which is a self-balancing ordered variant of the BST. B-trees play a critical role in database and file system indexing. Other notable variants include the AVL tree, which is a self-balancing BST and the prefix tree, which is specialized for handling text.
The first element added to a BST is the root of the tree. However, doing it this way means that it's a very simple matter to end up with a lopsided BST. If we simply insert a monotonically ascending or descending sequence of values, then the tree would essentially flatten down to a linked list, and we'd lose all the benefits that a BST is supposed to confer. Self-balancing variants of the BST exist in order to alleviate this exact problem.