It's pure laziness. That gunk gets in the tape and ruins the seal, it's not hard to wipe a blade off. It's the same mindset as someone who cooks on a filthy stove. Just basic attention to detail that separates a decent job from a sloppy one.

Fund adventures too, @the_shane, mine paid for the trip.

Check if you're using the right flour for your bread machine recipes. A lot of people grab all purpose when the recipe really needs bread flour for that gluten structure. Also, your yeast might be old and tired, that got me a few times. Even your oven's actual temperature could be way off from what the dial says. Don't just blame the timing, those little things can totally wreck a loaf.