This is not relevant to "Western" culture. It is relevant to US culture and East Asian culture, esp. Korea. Western includes Europe and South America, and these cultures are not as infantile.

Why? I have no idea.

I like that advertising mascots were mentioned, like the Geico lizard. I also think software tools like standard Adobe illustrator tend toward a cartoon infantile look. Probably as a side effect for the need to make things vector scalable. It tends toward a flat big shape paradigm.

It also could be that companies like the idea of the customers as dependant upon the product, and infantilization fosters dependancy

'The dictionary defines infantilizing as treating someone “as a child or in a way that denies their maturity in age or experience.”'

I don't know whether to laugh or be offended!