I've always assumed it's a nod to the original underground signage which had offset capital letters (https://upload.wikimedia.org/wikipedia/commons/3/33/London_

I've always assumed it's a nod to the original underground signage which had offset capital letters (https://upload.wikimedia.org/wikipedia/commons/3/33/London_Underground_Sign.JPG https://upload.wikimedia.org/wikipedia/commons/3/33/London_U...).