I sent an email to Insomniac games (Ratchet and Clank) to ask why so many developers make games with unskippable cut scenes. I got this reply:
Cutscenes are often used to mask loading and other things the system is doing in the background, which is a primary reasons they aren’t skippable in some games.
This isn’t an entirely satisfying answer because I think you can tell which cut scenes are actually playing over disc loading. They usually involve the spaceship flying to the next planet in Ratchet and Clank and even have a loading icon displayed. I understand these ones. The ones that are a problem are the story scenes that go on over a minute and you’re just trying to breeze past them to the point you were at before your son accidentally overwrote the savegame with a new one. (Playing games without being able to read can be understandably difficult.)