Logistics.
RB is not just selling DVD case sized units; it's also selling peripherals.
They want to sell hardware bundles and they wouldn't sell the standalone game until those were ready to ship as well.
That's 3 different sets of peripherals they need to produce to launch across 3 platforms.
3 separate launches will undoubtedly do better than one mixed launch which could see shortages in certain regions depending upon individual demand for each platform.







