Some routers do have 3/4/5 antenna directional antenna systems. I'm not sure if there's enough room or cost margin for an IoT device. If they were only directional then, I'm not sure they would help all that much, if there were other devices in the same direction (within 3km). However, there might be very short range differential (eg quadrapole) that could have faster than r^2 fall-off. The problem is that you're relying on all other devices in-band to do the same.

I think that's one of the reasons why unlicensed (ISM in the case of WiFi) spectrum is best used where the natural cell size (due to attenuation) is small.