Channel capacity depends on signal power, noise power, and bandwidth. Bandwidth and signal power are bounded by government regulations, but if you can make your antenna more selective (rejecting more noise) you can transfer more bits per second over a channel. MIMO/beamforming is one way to do this, and it is mostly limited by DSP power. Compute/watt isn't really increasing exponentially anymore, but it is still getting better, so we can still squeeze more capacity out of available bandwidth.
Think about it as your home wifi, it's essentially the same, how do you increase its capacity?
If the industry doesn't have to factor in ROI, then your argument is valid, but it's a business.