People must be buying what is advertised through commercials on the liberal news media networks. The news is geared to liberals not conservatives. The liberals buy the products to support the liberal news. The talking heads have to be talking head liberals or they must move to Fox. Public broadcasting is supported by liberal elected officials to get their message out through tax dollars.
Commercial free taxpayer subsidized broadcasting (NPR and Pacifica both receive tax funds as well as cheating the IRS with "non-partisan" 501c3 status they regularly violate) is dominated by the left.
With the morning/nightly news, people have grown lazy and fallen into a routine of watching the news (and watching the same broadcaster). It offers little actual news and what is there is liberal slanted and conservative bashing.
FOX News (local and cable) may be "better" but hardly fair to conservatives either. FOX was unwilling to call the election for Bush on November 2nd. There was no doubt. Even though they gave Bush Ohio, they denied crediting him with "known" states that would have given him the win.