Air fryers are convection ovens optimized for fast air replacement and high heated air throughput. So more heat gets lost to the environment because of the high air replacement rate. But that also means, moisture is extracted faster - and that is good for making stuff crispy.
If you often want crispy stuff, get an air fryer. If you often want to toast sliced bread, get a toaster. If you often want coffee, get a moka pot. If you often want tea, get an electric kettle. You can just use a combined convection microwave oven instead. But optimized tools are better for what they are optimized for.