Sorry, I didn't realize you were talking about the billboard on top of the building. The thread title says "marquee," so I thought everyone was talking about the marquee, which, as I said, only allows small signage on the sides.
The billboard is a different issue. I don't know for sure, but I'd guess it's the cost. I don't think that is operated by Roundabout, so it would be like purchasing any billboard space in Manhattan.
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