In the US, most toaster ovens I've seen have about 2-3 times the footprint of the average toaster, with additional height. This is actually pretty reasonable as you can use the toaster oven instead of the oven or microwave oven for many tasks (it's a less specialised tool than a toaster).
Last I read, US homes are the second largest in the world, after Australia. In Asia, many people live in apartments and that space is unavailable / non-negotiable. In addition, microwaves are not nearly so widely used.
And yet, every tiny apartment I visited in Korea and Japan had a toaster oven. The toaster oven is an incredibly useful and versatile tool that can stand in for bigger appliances, like full-sized ovens, in pinched spaces.
