I, too, have done this, strictly to see if it worked. It did.
I did it in March 2001, not exactly in high season. I came into Lahr, across the Rhein from Strasbourg, and went to the TI office. They sent me to a nearby hotel. It was simple, but very nice, and reasonably priced, what I look for. When I came down for breakfast the next morning, I discovered I was the only one there.
A few days later, I arrived in a little town in the Black Forest. I had a reservation for the next night, but I went to the TI office and they sent me to a hotel not too far away. Again, it was nice, but a little more expensive than where I stayed the following night.
I've stayed in that town three more times since then, the last two times were in a Privatzimmer closer to the station and less expensive than where the TI office sent me.
My conclusion was that, certainly in slow times, you can make this work, but the accommodations might not be as good as what you might have had if you booked them yourself in advance. There are people who do book ahead, and they get the choice of the best places; you get what's left. In slow times, there are a lot of good places. In busier times you might not be so lucky.