I would say that society has embraced being more childish and that the economic circumstances of a lot of western countries doesn't allow people to be independent, and leaves a lot of people in a state of suspended development on a social level.
In regards to a person who is autistic, I think that society is less judgmental (though discrimination still does go on), when it comes to viewing autistic folk and the social tendencies that are sometimes associated with that, i.e, being in touch with one's inner child or being behind one's developmental years in terms of years.
Those could be some of the reasons why being a bit weird or childish is considered to be more acceptable now, versus say, a few decades ago.