The microwave in my house is built into the oven.

This provides absolutely zero advantages to the oven or to the microwave. It does cause a lot of stupid, easily foreseeable problems:

- There's only one control panel, and if the oven is currently active, some of the microwave controls get disabled.

- The microwave is awful in various ways -- regardless of whether the oven is active -- which wouldn't ordinarily be a problem, because microwaves are very cheap. But...

- It's impossible to replace the microwave, a $50 device, without simultaneously replacing the oven, a $2000 device.