Well, I recently joined a tennis cursus for beginners since I had never played tennis before and I must say, the atmosphere during tennis is a lot different from badminton. I also have a feeling that tennis used to be a more “elitair” sport than badminton.
That might be why people take breaks everytime one of the player so much as farts.

On the other hand, Tennis is heavier on the arms than badminton, especially when playing on a high level, though I don't at all.
Unlike the shuttle which deccelerates quite quickly, you have to counter all the punch your opponent puts in a tennis ball to hit the ball back.

Then again that is little excuse for professionals to appear almost lazy to the eyes of a badminton player.