I never used to butter my waffles. To me it was added fat that I could not taste. Mind you, we are talking about a habit that stretches back to my early childhood, so who knows if I really could taste the butter or not. And then I was talking to a friend, who commented that the point was not the fat so much as salty richness in counterpoint to the sweet maple.
Oh. Now there was something I had not considered. But when I went to do it, it just still seemed pointless, trying to evenly spread the butter into those holes. And then inevitably, the maple syrup would be cold from the fridge, because I usually forget to take it out in advance, and it would stop the butter from melting and make the waffles cool off (OK, here is where I confess I was raised on the fake corn syrup stuff that does not need to be refrigerated, so about the time I started experimenting with butter I also started experimenting with real maple syrup). It just made so much more sense to me to melt them together and use them hot.