And they are being outsold 100-to-1 by noname WiFi based gear, which unlike them, works on day 1 — a thing most people want, hence the sales success.
Proprietary systems by far established a reputation for themselves as "doesn't work with anything, even itself."
WiFi is not a candy either, and for most people it means an increasingly mounting pile of one per-device apps, but that's definitely better than not having the device working at all after every homekit/google home update.
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.
No if you want secure, local control of your home automation you want Zigbee and Zwave devices not WiFi.
There is a TON of these devices on the market, and not just ikea like your other post seems to suggest
Hue works extremely well with a Hue hub. But it’s even better to get a non-proprietary hub to connect your devices.