I put myself in the 75% category, though actual analysis might prove it to be slightly less - but the numbers aren't all that important, as the replies here seem to indicate, it's the mentality ... I sail as much as the conditions will permit. I do moor in a busy, south-flowing tidal river with medium current and the wind is typically SW, making it very difficult to sail out of my (south facing) slip. And let me tell you that the ferry captains are very intolerant of sailing 'purists' who tack across the main shipping channel. Don't be surprised if they plan their CPA's to put a ferry on either side of you, stealing your wind and bouncing you around in their wakes like a teddybear in a washing machine. So the engine is important for safety, and to make getting to a point where sailing is possible in the first place. But as soon as I can, the sails are up, and even if the wind is light, we poke along without the engine.
But there's something fundamental being missed in the responses to this poll, and it's the same thing that makes the Coasties train all the cadets in engineless sailboats ... and that is that sailing forces you to be more aware of the wind, current, tide, other boaters and anything that might make it difficult for you to get where you're going under sail. It makes you consider all of the conditions in your cruising area, in a way that powerboaters and those with the tendancy to motor a lot don't have to. Why worry about the tide change if your just going to power in anyway? It makes a self-fulfilling prophecy in a way ... you can motor, so you will go out in less than optimal conditions, so you will get to the point where you need to motor.