This might just be because it's a demo, but man are things ever fast... they open up a document and it just instantly comes up. They load a video and bam, instant. There's a little segment where Bill Gates is showing off opening up multiple instances of Excel and they open up so quickly. I tried opening up Excel on my desktop PC and the speed is nowhere close to what this video is showing. I open up a document nowadays and there's a splash screen, there's some lag as the application checks if there's an update, the application appears and the layout starts to jitter and flicker... none of that is in this demo.

Obviously some of this is for show, but even still it indicates people cared about having a very smooth and snappy user experience back then and that it was absolutely important to showcase performance. Somewhere along the way developers just quietly agreed that latency is the user's problem.