To further clarify/prove the point, I watch streaming trades action at another site, it's 15 minutes delayed, but day after day, the sell column goes at the current bid that moment, ditto the buy column on the ask.

If one is "impatient" and puts in market orders either way, the MM's will do you the favor...lol.

They make their money on the spread between B/A.

There is also the need for people to make sure a sell or buy excecutes immediately, and if that is their trading style so be it.