And in inclement conditions, it can make the difference between losing control of your vehicle or not. When you brake, you decrease your steering ability in most cars. Fine when its calm and sunny in CA, not so much when it's icing over near Ashland OR on the pass.
My point is, it feels safer and easier to aim to enter a new lane with the aim of "following" someone, rather than trying to rush in "ahead" of someone. But maybe it's just me.