Who would want this Amazon product for every light switch, remote control, and thermostat? No, most buyers will probably just buy one for a household. In that case, I agree that a regular tablet would suffice.
My point was that you have a remote control already; you don't use a tablet instead of that, just for use as a remote control. In a similar way, a tablet might be overkill for a 'home assistant', and the Amazon Echo seems designed to address that.