I’ve done this too, I admit. (OMG, slide 22!).
The thing is, I find whenever I have to write on the board in a lecture setting, it slows me down so incredibly that I never get through my material–when I time my talks, I always tend to time them by how long it takes me to talk the talk, not how long it takes my atrophied and ill-accustomed-to-actual-handwriting little left hand to squeeze the words out and onto a board. But…then I fall into these traps. A lot of them, actually.
Mea culpa, mea culpa, mea maxima culpa.