Why should the government fund the arts?

I mean the idea of art is to express creative freedom. So if the government funds your art, then you're expected to create art that furthers that government party's agenda. So how can you call that art "freedom of expression" if the government is paying for it and telling you what to create? Doesn't that make you nothing more than a commissioned worker for the government and not really an artist at all? How can you call yourself free?