They only get a new parade when they figure out how to reuse that castle float that has been rolling down Main Street since 1996.
This may be a dumb question, but where is SpectroMagic stored right now? The original Main Street Electrical Parade has been shuttled back and forth almost continuously from California to Florida in the past decade, and the Magic Kingdom's original MSEP ended up in Paris (then probably scrapped, I guess?). SpectroMagic has never been taken to another Disney park, so it must just be gathering dust somewhere on property. I just didn't think Disney had that much space for floats (remember they have to store the Christmas floats and whatever is left of the Easter parade floats) that it could just store a dormant parade indefinitely.