Main Street was an unbelievable Legend set. With so many of the classic 80s and 90s Town sets being mostly simpler bricks and plates and with all the AFOLs coming out of the woodwork at every thread concerning Legends, it makes no sense why at least A FEW Legend sets aren't available.
But then in another sense, I guess it does make sense. Lego was down financially a few years ago, laid off a lot of workers, which reduced their manufacturing capacity.
Now in the least year or two, Lego has done better, but supply isn't meeting demand (and now seeing backordered sets on SAH is a regular occurance). Hopefully Lego can get back on it's feet into growth, then maybe we'll see more and more sets.
Notice the sets they're releasing are the ones that sell BIG (and not just to AFOLs).