Games need to have in-game options for increasing or decreasing the size of text used in the game. Anybody who argues against such options are wrong; you simply can't predict every gamer's needs and situations.
I agree it would be great to have this, but it's not a trivial amount of work.
And is this just for dialog? Or do we need to do it for buttons and every other UI element?
Just localizing into German already breaks just about every piece of UI during a game's development, and font size options would be even worse. I can't even begin to imagine the horrors that variable font sizes and German would wreak on UI programmers and artists...
Again, not impossible, but a huge amount of work for something that isn't really affecting that many people, since most people that play games are young and sit appropriate distances from their televisions.