When the mempool empties, why don't miners mine the 0.999 sat/vB TXNs?

I realize that MOST nodes don't relay TXNs below 1 sat/vB, but obviously some do. So, if a miner has access to any TXN from 0.5 sat/vB to 0.9 sat/vB, why wouldn't they mine them when it is all that is left?Looking at https://bit.ly/2FtQzra on Sept 8/9 the < 1 sat/vB band looks unchanged, even when the > 1 sat/vB band completely empties. I know miners are very focused on profits, so why leave this money on the table?Or perhaps that whole band is almost 99.999% TXNs set to 0.000 sat/vB. In that case the few TXNs set to 0.9 sat/vB wouldn't even register on the display.Thoughts? via /r/Bitcoin https://bit.ly/2Flh2as