I assume it's cheaper to build it above instead of below.

Neighboring 77 Hudson also has a large above ground garage but it still manages to have retail space that adds to the neighborhood (a small grocer, cafe shop, and a bar). Which is why I said many of the buildings in the surrounding area aren't great but they still manage to do more to help create a neighborhood. While a neighborhood full of 99 Hudson's would be a bleak place.