A lot of children simply don't realize they can't see clearly, because they don't have a good frame of reference to compare their current sight to. A lot of these children only get glasses once they start having to actively read- with parents or teachers noticing excessive squinting or other altered behaviors. I'm not sure about this boy in his case, but a higher hyperopic prescription like his usually is not a rapid onset sort of thing, but something that could have been there from an early age. It could be that they didn't catch it until now or couldn't get glasses that would fit him until the video was taken. A lot of young toddlers simply refuse to wear glasses as well (regardless of whether they have the right size of frames for them or not).