[InclinedPlane]

" As receiver electronics have gotten better, more selective and more error tolerant, these margin spaces became less necessary..."

More to the point, as the technology used to broadcast has completely changed from analog to digital the margin spaces have become completely unnecessary. Additionally, digital television does not use the entire spectrum previously allocated to analog broadcasts.

Edit: additionally, in locations where there aren't local television broadcasts on certain channels those channels can be used for wifi.

[mikemol]

Digital signal transmission tends to include an increase in error tolerance, which I mentioned. The margin reduces the strain on the error tolerance, which is also needed to cope with signal loss issues.

So, no, the margin spaces aren't completely unnecessary with digital signaling.

Furthermore, I'll pick a couple nits and point out that it's only television broadcasting which has completely switched to digital in the US. AM/FM radio is still analog by definition, and there are large swaths of spectrum which use those and other signaling methods.