Well, that's the orbital speed required for their LEO orbit. In order to deorbit, they have to bleed that speed with a deorbit burn first in order to put them selves into a re-entry trajectory.
Not all of that speed is lost via friction in reentry.
The vast majority of it is. The delta-V from the de-orbit OMS burn is only around 250 ft/sec, and the shuttle actually accelerates and hits its top speed as it falls into the atmosphere after the OMS burn.