It depends on what you use the firearm for. I agree they look better without a rail but all of my firearms have a light attached and my 1911's are no different.
I carry a 1911 as a duty weapon every day so it just makes sense for them to have a light. Remember, a weapon light doesn't add much weight so my reasoning is why wouldn't you want to have it if you happened to need it? Just like carrying a firearm, you hope you won't need to use it but you'd rather have it and not need it.
Off duty I carry my full sized 1911 with a TLR-1 HL in a Raven Concealment IWB holster.