The use of RF frequencies to broadcast TV content is by far the best way to deliver that content for a certain subset of programs that cover live events for huge audiences[1]. Serving that stuff over IP would be a real challenge. I'd prefer it if we could keep a few RF broadcast channels around but move all the Family Guy and Top Gear re-runs onto on-demand IP based systems.
[1] Things like major sporting events, Saturday night talent show finals, large scale news events e.g. 9/11, Christmas specials and key episodes of certain soap operas.