I can understand the temptation to throw daily homework away (though I don't do it.) Teachers are busy, busy people, and to sort and file 40 or more sheets (2 homework assignments x 20+ students) every day until it can be sent home, is time consuming. Some teachers let students sort and file corrected homework, but I find it becomes a privacy issue, and I am the only one who handles student work of any kind. When I was a new teacher, before I started using the "magic number" system and had students file EVERYTHING in numerical order, corrected homework would accumulate in a huge chaotic mess until I could sort and file it. Maybe if you send corrected homework home every day, handling it would not be such a hassle?