You wouldn't get additional sales from the feature. It's not worth retrofitting to the 1S (they'd have to develop a transfer/backup app as well as adding cost to the console to add a user accessible drive). It makes little sense to add it to 1S. It makes plenty of sense to add it to a new console to offer a better user experience and keep users happier, especially if the starting storage option is very limited and you need faster, low latency access. As described before, something as straight forward as an M.2 slot behind a lift-up flap will be idiot-proof. Users won't gain anything by the internal being fixed, but will gain if it's user replaceable, so there's no sane reason to argue against its inclusion. It's been proven to work in former PlayStations so there are no concerns there, and SSD capacity and price should change dramatically over the 5+ years of the console being around.