Physically delivered coins are probably being accumulated by investors and removed from the market for longer term investment. The vast majority however are just sloshing back and forth, being traded by short term speculators. Those traders don't get coins delivered. They roll forward their positions into the next monthly contract instead.
I can't find officially reported cumulative volume from the ICE but you can see the daily volume on monthly contracts here: https://www.theice.com/products/72035464/Bakkt-Bitcoin-USD-Monthly-Futures/data?marketId=6137618
So ~3K-4K BTC volume on each of the front two contracts.
This is a snapshot of USD volume over the past month: