“Cutting in” at the last moment is what you’re supposed to do. If the traffic flow dictated everyone to merge earlier, they would make the merge earlier. This entire thread is filled with confidently incorrect. Yes, you’re supposed to “let” people in. And yes, they’re supposed to drive at the speed limit (“speed wildly”) in the alternate lane until the merge.

You yield to the merging traffic because that’s how it’s supposed to work. You have no moral superiority about it. It’s just that one of you (not you) knows how to obey traffic laws and guidance, and one of you (you) is doing what they’re supposed to because you think you’re being charitable.