Traditional Unicorn architecture involves a front door several feet above the ground. In the olden days it was so that Unicorns could look down on anyone that came to visit them and make sure that teleportation was the only dignified way to enter a house. In the modern days Canterlot building codes require a set of stairs if the doorway is raised up. Many Unicorn nobles still take advantage of the height advantage to look down on anyone who comes to their door.
Princess Celestia, who could rant for hours and hours about stupid Unicorn traditions, actually liked this particular one. It meant that she didn’t have to hurt her neck looking down whenever she visited those houses. It put her more or less at eye-level with the ponies she talked to. At least until she was invited into the building for tea. It was always tea. Never coffee. Never ice tea. Never cookies. Always tea. Never even cake! Ponies even knew she liked cake. But no, always tea.