Please see BST codes below. It only outputs "5". what did I do wrong?

#include <iostream>

class bst {
 public:
  bst(const int& numb) : root(new node(numb)) {}

  void insert(const int& numb) {
    root->insert(new node(numb), root);
  }

  void inorder() {
    root->inorder(root);
  }

 private:
  class node {
   public:
    node(const int& numb) : left(NULL), right(NULL) {
      value = numb;
    }

    void insert(node* insertion, node* position) {
      if (position == NULL) position = insertion;
      else if (insertion->value > position->value)
        insert(insertion, position->right);
      else if (insertion->value < position->value)
        insert(insertion, position->left);
    }

    void inorder(node* tree) {
      if (tree == NULL)
        return;
      inorder(tree->left);
      std::cout << tree->value << std::endl;
      inorder(tree->right); 
    }
  private:
    node* left;
    node* right;
    int value;
  };

  node* root;
};

int main() {
  bst tree(5);
  tree.insert(4);
  tree.insert(2);
  tree.insert(10);
  tree.insert(14);
  tree.inorder();
  return 0;
}