it's about being able to read emotions:

a large portion of autistic people have trouble reading emotions in others.

that's why they're often drawn to things like books, comics, animated content, theater, and, like in this example, robots that clearly express their emotions.

speaking for myself (diagnosed ASD), it's the ambiguity that bothers me more than anything. i like it when things are nice and clear, neatly organized, and generally don't require a lot of attention to interpret.

interpreting the environment is taxing enough, adding a lot of emotional interpreting on top can quickly get overwhelming, which leads to poor mood, performance, and ultimately just straight-up headaches...again, this isn't a hunch, it was part of the ASD diagnostic test.

so i can imagine how much easier it is for kids with similar problems to relate emotionally to something that shows it's emotions in clear, easily recognizable ways, rather than having to guess constantly. that constant guessing gets real tiring, real quick...

I'm sure it worked for some and not for others.