I'd argue that this isn't the same for every teacher. Strong procedures and high expectations can sometimes mean that kids do work even without their teacher there; however, many teachers, including myself, have students controlled, contained, and peace is hanging by a thread in some periods. The removal of the teacher from that equation leads to an eruption of unproductivity. I hate being out (except when it's amazing because I can sleep in and get so much done) because I feel like I'm losing a day. Does that reflect poorly on me? Yes.
Every time i'm out I get a call about my 6th period playing music, fighting, yelling at the sub, and everything in between. Is that me or my kids? 50/50? I'll take 50/50. It's a small wonder subs keep coming to my school. I wouldn't.