Where I am, they had popped up all over the place at first but have mostly disappeared since then and the ones that remain barely have any flavour customizations anymore.

My guess would be that they came with predatory subscription fees or some shit like that that resulted in them costing more than they brought in and most businesses cancelled their subscription or downgraded to the basic version that just acts as a shitty version of the old style.

Either that or they are difficult to keep clean and result in a lot of flavour syrup going to waste when the less popular flavours expire. Or a combination of the two, maybe with HP-style machine-enforced expiry dates on the syrups that are tuned for profit rather than safety/quality.