Tall Gate

Two practical reasons. It is tall enough to ride a mount straight through without dismounting, which starts mattering the moment you are hopping on and off something fast every time you leave the house. And it slides rather than swinging out, so you can pack blocks and furniture flush against both sides and it will still work. Normal doors need clear space to swing into, and a chest in the wrong spot jams them shut.

Fighter AI enemies bash doors open during events, and one of these takes noticeably more punishment before it gives way. It still counts as the door a house needs and NPCs still walk through it as normal, so there is no cost to using them across a base you expect to get attacked.

There is exactly one style. Every furniture theme in the game has a matching door, and none of them have a matching gate, so a themed build ends up with a plain metal gate sitting in the middle of it. The inventory sprite is also misleading: it shows the gate face on, which is never how it looks once placed.