You might simply forget to do it, or the idea might simply not occur to you unless there are enough surprising events going to follow every morning. Or, if the idea occurs to you, it might be because there are a couple surprising events followed by a scary event that causes you to abandon the idea. (À la “do not mess with time”, but less obvious.) The space of possible stable time loops is huge.

Also, like somebody mentioned, it might not be perfect. It probably doesn’t work within Azkhaban, for example. The producer might simply make it “good enough” and expect that most people won’t bother to ask for their money back.