That lack of volume is a Coinbase reporting error, or something fishy up with Coinbase. The same pattern can be seen for ETHUSD and LTCUSD on Coinbase as well.
BCHUSD is the only one which shows volume during the time period starting Dec 21, as BCH was added to Coinbase on Dec 20th.
BCHUSD is the only one which shows volume during the time period starting Dec 21, as BCH was added to Coinbase on Dec 20th.