They say "a picture is worth a thousand words" which means that a single image can often convey an idea/subject much more effectively than trying to describe it. Imagine it's someones birthday, wedding, retirement or anniversary and you just want to remind them of some of the amazing moments you've shared. You could tell them about those moments or you could show them.
Caricatures picture books can also help keep people awake during speeches and presentations. Now if you're the best man at a wedding, the possibilities are hilariously endless.