The only time I've ever had to do this is playing around Extirpate. In the particular scenario that came up, my opponent had just milled a large portion of my deck, including a lightning bolt (me playing burn). I had two more in my hand. If I cast one and try to let it resolve, my opponent can Extirpate Lightning Bolt and remove the other from my hand. My best option is to dump both of them on the stack before giving my opponent priority.
Split Second is unique in that it doesn't let you respond to it, so effects that don't use the stack or otherwise shut down the stack until they resolve are a good place to look, even if it might end up a little contrived. Imagine a Manifested Void Winnower. Since flipping it face up is a special action that doesn't use the stack, the opponent can do it as soon as they get priority, immediately shutting me down from casting any even-CMC spells. In that case, if I have know it's there, and I have two spells I need to cast, I should put both of them on the stack before giving priority.
However, you are correct; 90% of the time it is correct to cast, wait to resolve, then cast the next spell. The examples I gave were very much corner cases, and the second one I'm fairly confident will never happen in a game.