RE:RE:wall?Just because there is a sell doesn't mean it is a retail seller selling to a retail buyer. If no retail buyers are available at the current prices the market makers step in to maintain liquidity. Back in the day these individuals were called specialists.
Long story short, the market makers determine the bid ask spreads and it matters not whether they are buying/selling for their house accouts or to fill retail orders - they try to maintain liquidity based upon general supply/demand for the particular issuer.