who_cares, a sequence is a dynamic thing. A gap opens up ahead of you because someone does better than expected or takes track shortening when it wasn't sure they could earlier. By moving you up a bit to fill that gap everyone behind you benefits too. The aim is to maximise the entire sequence & is not just considering one aircraft - individual aircraft get tweaked to achieve this.
Sure, a 3 minute gap could be left in the sequence instead of speeding you up but how is that efficient for the system as a whole?