Because nobody wants to shell out for 2 pairs of tickets knowing with certainty that one of them won't happen. Is Ticketmaster going to refund all the fees? Good luck with that. It's already annoying everyone just to have to look at 2 seats maps to figure out where to sit, now people have to through 2 transactions and prepay for double the tickets? Because uncertainty tends to suppress purchases and you're basically guaranteeing a less filled stadium either way? Because maybe Citi Field management and their employees have better things to do than just keep everything on hold indefinitely for our preferences? Because maybe the TV people want to know where to send their equipment trucks more than a couple days ahead? Because maybe the best way to have a good field at Citi is to lay sod several days in advance but nobody wants to pay for that if we switch back to YS 3 days before the game?
Have you never been involved in any sort of event that required planning and seen how hard it is to arrange logistics for the simplest things? Why do people think the logistics of leasing and prepping 2 stadiums at the last minute is no big deal? Try planning a toddler birthday party without deciding where it is - not even what county -- until 3 days before it happens. This is ludicrous.