Assuming a restaurant doesn't have a cellar, then inevitably wine will not be stored at the proper temperature - and this is a significant issue with the slower moving, more expensive wines on the list.
Whether or not a restaurant has a cellar, they also need to ensure the wine is served at the correct temperature. This is relatively easy with white - you just put what you expect to serve that night in the fridge - and it will only not work out if you have a run on one particular wine, but ice buckets will do the trick and, assuming your staff are knowledgeable, can be done behind the scenes easily enough.
The problem comes with reds - they are not appropriate for a fridge as then they'd be too cold. But they will need to be chilled to around 15 degrees, so either you need a cool storage space (perhaps where the fruit and veg are kept) or some other technique to get them to the correct temperature, absent other specific wine refrigeration. And then you have a similar problem as with the whites - what happens if there's a run on an unusual wine? It's even more difficult to get a red to proper temperature quickly.