The trouble with that is just before you have to stop you ride over a little bump and realize that you just clipped back in accidentally, and there is no time to unclip now.

That's my biggest beef with clipless pedals. In urban riding environment, I have many longish stretches when I'm going slowly and might have to stop or accelerate on a dime (e.g., careful lane-splitting, crawling up to a left turn). Unclip too early - and you have to place you foot in a cumbersome position or risk accidental clippilng in. Unclip too late - and we all know what the consequences are.