I've never seen a countertop oven, except as a "feature" of an expensive microwave. As I understand it, results for baking especially would be poor, as the oven has less air mass and less heat capacity.
(At least, that's the reason my mum gave for not using the feature on her fancy microwave. She used to be a professional cook.)
Besides the price, the low thermal mass is a selling point -- throw a couple chocolate chip cookies in there and you don't heat up the entire house in the middle of summer just for a fresh baked treat.
I forgot to say I've lived mostly in the UK. A quick search shows a couple of models are available, but that's a tiny selection compared to most appliances, and they're being sold at a very low budget shop.
Britain doesn't really have snack food like America. I've never thought to warm up a cookie, and without air conditioning I doubt I'd want a warm snack in the summer. Ice cream!
(Or, perhaps with smaller houses on average people don't want to use up the space for one, and wealthier people with space don't want to heat up processed foods.)