Low fees have prompted a huge amount of defragging, much of it at 1 sat/byte: this one for example consolidating tiny 824 satoshi dust particles.
The UTXO has consolidated from 67.5 million to 55 million. At a rough guess, for the last several weeks about a quarter of daily volume (by MB) has been this ‘backlog’ of defragging (backlog from when high fees made it too expensive). Consolidating 12.5 million bits of dust at 148 bytes per input fills getting on for 2,000 blocks – almost 2 weeks’ worth of traffic.
When the defrag backlog is done, and now we have segwit and batching, transacting at 1 sat/byte knowing you’ll get into the next few blocks could become the norm again.