Just like block 910264, there are 2531 transactions there but there are only four transactions that have fee below 1 sat/bytes which is very small to me. Maybe this will increase if more wallets are supporting fee below 1 sat/vbyte.
I just checked the most recent block.
Block number 910280 included 5,026 transactions and 3,853 out of them have been made with the fee rate of less than 1 sat/vbyte.
Not not miners accept transactions paying less than 1 sat/vbyte. That's why some blocks include transactions paying less than 1 sat/vbyte as fee and some don't.