I would love to see some real sale stats if those claims are real? I have no idea how much they are supposidly outselling zigbee or z-wave devices.
From a purley anecdotal standpoint, you start with the wifi devices as they are low barrier to entry, (no hub required and normally comes with some sketchy 3rd part app); If you decide to go all in and buy more than a handful you naturally progress towards the zigbee/z-wave devices and ether a fully managed Proprietary "do it for me" system like SmartThings, or you go down the self managed route with HomeAssistant or OpenHAB.
From a purley anecdotal standpoint, you start with the wifi devices as they are low barrier to entry, (no hub required and normally comes with some sketchy 3rd part app); If you decide to go all in and buy more than a handful you naturally progress towards the zigbee/z-wave devices and ether a fully managed Proprietary "do it for me" system like SmartThings, or you go down the self managed route with HomeAssistant or OpenHAB.