When I mow on mulch, I get tons of grass clippings trailing behind. Why?

When I mow on mulch, I get tons of grass clippings trailing behind. Why? - 1
Added (1). I have a good Honda, self propelled mower, set to mulch. When I'm cutting I always end up with a think line of grass clippings in the lines of my tires. I then have to rake, which I shouldn't have to do.

Is there something wrong with my mower, or my technique? I've tried going slower, raising the height and nothing seems to work.

Read more: When I mow on mulch, I get tons of grass clippings trailing behind. Why?