The microwave example just doesn't make sense when what you have isn't a single "just push the power button" machine, but a combined microwave/oven for instance. You'll want clear mode management, temperature management when defrosting meat, pre-heating and convection when cooking a whole chicken etc.
Anecdotally, a lot of people don't really understand/care about bicycle gears, and stick it to the heaviest and call it a day (on city bikes it's not that heavy, they can dance when it's tougher, and just get off and push the bike when it's really hard). We've seen the same cycle for cars, where people only caring about going from A to B will enjoy automatic transmissions better.
All in all, I agree single purpose products are great when you can afford one and it does the job. Paradoxically it also helps expand the use cases as the user comes to better understand how it works and how it can be "abused".