Because much though I like you closing security holes (and offering me new functionality), I do not like having things pop up whenever I open your app (or when I'm doing other stuff).
VLC, I'm particularly looking at you, with your download dialog box that overlays the screen that's playing the video I just double-clicked, and makes it impossible to click pause while the updates is downloading. Seriously. What the fuck?
Original post on Dreamwidth - there are comments there.