And it moves way more air than a normal oven, thus removing water vapor faster. This water vapor that partly steams the food, resulting in moisture saturated air that in turn prevents more moisture from escaping, is the main difference between a frying pan and an oven. A deep fryer replaces the water with oil, an air fryer just extracts the water quicker. Both prevent the food from cooking in water or steam, resulting in a crispy texture.
The clean function locks the door, cranks up the heat, and burns off all the crud in the oven. You can vacuum any ashes left after it cools down. Its awesome if you're lazy like me. I have zero interest in bringing out the Easy Off and elbow length rubber gloves.
Oh, yeah. It's been a long while since I've lived in that environment. You're probably right that most cheap stand-alone stovetop/oven units don't have a convection setting.
I've seen them commonly in homes in Europe, but I've not seen them once in the US. But even convection ovens are not as effective as air fryers because they're not as efficiently designed. They use the same principle, but the shape and fan power to volume ratio in air fryers is much better. Also, not all air fryers are the same, some are way more effective than others.
Most people don't even know how to use their microwave properly. You really think they know how to use their convection oven properly? It's not WHAT it does, it's that an air fryer is usually simple and has shit like "turn dial here to cook a chicken".
People like it because they don't know what they're doing and it does it for them.
I'm not here to convert you, but this is just as dismissive as OP. Yes it's a convection oven. We also have a full size convection oven. It does not cook things as dramatically faster as an air fryer does. It's not the same experience at all.
I say this as someone who literally said, "so it's just a small convection oven" until we got one. We have used it literally every day since getting it ~2 years ago.
It's not just any of these things:
Toaster oven
Small convection oven
Small oven
There is so much air moving around in an air fryer that parchment paper without food holding it down gets immediately sucked against the circulating fan filter (which we learned the hard way) and lighter bits of food (like cooked bacon that you might toss in for a quick reheat) will swirl around inside the cook basket.
It may not be for everyone, but it absolutely does cook food faster than in a regular oven, sometimes by an astonishing amount. We have a short but significant list of things that we also think are noticeably better from an air fryer, and nothing I can think of that we've tried comes out worse.
Frozen stuff works great, everything from fries to eggrolls.
You will start to get an idea how long things take after you have it. Many things now have airfryer instructions, or there are lots of "how to make xxx in an airfryer" articles.
Generic airfryer instructions are usually pretty close for ours, but any given model may have its own cookbook with times for different sorts of things (ours does) and after awhile you'll get a feel for how to nudge generic instructions to fit your model.
For a very small number of specific kinds of breaded things, I'll spritz them with cooking spray when they go in to help them get more like they were fried in oil, but that's really personal preference and I only do it on a couple of things.
Get one with a big enough basket. Things need to be cooked in a single layer. You can pack it pretty full, but single layer is important.
This is the big thing. So many times we want to heat up some left-overs and that would turn soggy in a microwave, but heating up the oven to reheat a few square inches of food is a vast waste of energy.
These take up a lot of space, though. I think one of those double ovens, where one is only tall enough for one tray, would be ideal. Convection, of course, but I haven't seen a built-in without a convection mode in years.
And convects much more powerfully and efficiently since it's shaped like a cylinder instead of a cube and the fan strength to volume ratio is way better.