No, because those devices have little or no controls and those controls are easily bypassed and/or not honored by the platform.

I think they should. Theres a fine line between beneficial and detrimental. I had a 3DS growing up and could browse the web with its very gimped browser, and I think something like that is actually very good for a child (able to access the internet and view simple and informative sites while being too limited to access social media and the like)

The problem is unrestricted access to mobile devices. A game console or desktop PC isn't as big of a deal.

Have you ever visited any game store and turned off nsfw protection?

I love gaming, but I hate all the smutt games. It discredits the medium, essentially what has also happened to anime.