Because if you are three you cannot read well enough or quickly enough, or for long enough to make the experience worth the effort. If you have a super kid who can, then awesome. Some kids can read at that age a little. But that is reading like "see the red ball". You show a three year old a wall of text, it is not getting read.
So, he is reading it to her, which makes changing the text completely pointless.
The time spent doing a text change which is completely unnecessary then? Well could have drawn a picture, or taken her to the park to play on the swings or even got some rest so that he was in a better mood to play with her the next day and didn't spend his time playing video games he wanted to play when he should have been spending time with her.
That sort of stuff.