Politicians rarely know when there is a problem, someone has to tell them there is one. There's where a lobby group comes into play. The danger becomes which one do you believe? You can hear both sides and make a carefully thought out decisions, and then do that for the 10,000 other groups coming to you, but it's a time consuming process.

I agree with your conclusion, but not your premise. As a politician it could be very dangerous to simply ignore a lobbyist.