Even the Wikipedia article points out sweet muffins are only really different in that they’re usually not frosted and I’ve seen plenty of bakeries do that too.
They may have once been different, but modern American muffins and the mixes bought in stores frequently have more sugar than cake batter while using the same ingredients. They’re just breakfast cake.
They’re quickbreads, actually. To be pedantic though, cakes are technically very sweet quickbreads with a different order of ingredient mixing.
Even the Wikipedia article points out sweet muffins are only really different in that they’re usually not frosted and I’ve seen plenty of bakeries do that too.
They may have once been different, but modern American muffins and the mixes bought in stores frequently have more sugar than cake batter while using the same ingredients. They’re just breakfast cake.