Why do I need SwitchBot Hub to be WiFi compatible?

Hello, I've been looking into purchasing a SwitchBot Bot recently but I have been on the fence since it does not have WiFi capability without purchasing the Hub - which is an extra $39 on top of the $29 for the Bot. 

I don't understand why can't these just come with WiFi capability out of the box? I have other IoT devices (i.e. smart plugs) that I can control from anywhere there's internet. Why couldn't the Bot do the same?

The hub seems like a hard sell for someone who's only looking to buy one or even two SwitchBot devices.