>>1475866After the loss of Challenger, the STS largely stopped doing commercial satellite launches, with its payload being mostly NASA/DOD/other government launches.
http://rammb.cira.colostate.edu/dev/hillger/Shuttle-related.htmhttps://history.nasa.gov/pocketstats/sect B/P&E.pdf
Before that, the US government subsidized commercial users of the STS, but was still undercut by Arianespace.