One barrier to bentos for a lot of people might be the whole idea of eating cooked food that's cold, or at room temperature. The basic bento in Japan is meant to be eaten at room temperature, and is still very tasty (insulated/keep-hot bento containers are not that widespread in use, despite the efforts of manufacturers). Aside from some food that's designated otherwise, we are geared to thinking that food that's cooked should be hot. It's true that food that's meant to be eaten hot can taste blah when cold. There are some tricks to use when making food that you intend to eat in a non-heated bento though.