The TV license is certainly bit ridiculous, but being legally blind doesn't necessarily mean you can't see at all, just you fall below the legal threshold where it's judged that poor sight will interfere with your day-to-day life. Lots of people registered as blind can still watch the TV just fine even if they won't be able to see the detail.
The threshold is a lot higher than people think. I would be at the level of legal blindness without my glasses. I use my phone without glasses daily. A small laptop screen without glasses would be alright too, but desktop monitors are too big.
Of course, to be considered legally blind, your vision has to be that bad with the best correction available. (Below 20/200)