You probably noticed, but each of these is also just a quote from the paragraph right next to them. Also here the drawings are cute, so that's nice.

Maybe you're not used to that style, but it's pretty common in educational literature (especially for younger audiences). They're mostly navigation aids, highlight conclusions or other important tidbits, or merely exist to break up the flow so it's not just an impenetrable-looking block of text.

I remember many school books being full of these back in the day.

Some newspapers do it too, where they just place a quote from the article itself under images or just enlarged by itself, not really adding anything in either case.