Radio modulation / coding (at least for 802.11) benefits greatly from paralelism (lots of matrix multiplication etc).

I imagine that using an ASIC is way more cost efficient vs using a CPU.

One example is the introduction of MIMO, a technique to send multiple data streams in the same frequency band in parallel. This requires multiple antennas, i.e. hardware which wasn't there in the previous wifi version. Note this was 2009.