I'm sure it has more to do with fan behaviour during those events than the actual time itself, regardless of what they say. They probably found that fans tend to flip channels or become otherwise disengaged when it happens.
I don't care about the intentional walk rule either way. I absolutely HATED seeing 3 or 4 pitcher changes in an inning with each guy facing one batter. Maybe it doesn't happen often, but it stands out when it does. It grinds the game to a halt.