Beyond babies they'd be handy! I remember taking road trips with my parents (driving to Florida, etc.) and watching TV in the back seat and could never get rid of that annoying glare on the screen! So, my brother and I would shimmy blankets in the windows to cut down on the glare! It was all about the comfort....ya know?!?!?
Take it from the kid who got carsick on every family trip until the age of 14.
Not being able to see out makes motion sickness WORSE, drastically!
At least when you can see out, your eyes back up what your inner ear tells you.
Without the visual cue that you're moving, your stomach and inner ear go straight to DEFCON 1, splat-city!