Musicians, actors, dancers, and other performers know how much preparation and practice goes into their few minutes (or a few hours) of actual performing. Consider a single dancer in a 1.5 hour performance. A professional 25-year-old dancer has probably been dancing since they were around 5, and they’ve logged thousands of hours practicing dance, and probably another few hundred preparing for this single performance. Before they learned the dance, the choreographer, who has also probably been dancing for the same amount of time, but has spent significant amount practicing coming up with new choreography, spent tens if not hundreds of hours coming with the choreography to be taught for this performance.
Same with scientists - hours of work and preparation go into just the technical aspects of a manuscript, grant, or technical presentation, and even more time goes into editing, wordsmithing, and perfecting the delivery. But here the performance is the text, which must stand alone for all eternity as the written manifestation of this work.
Why do we spend so much time before the actual performance? Because it’s only the performance that people see and remember. If they see an uninspired performance of dull choreography, they’ll remember that and not want to see that show/dancers/choreographer again. If they see a crappy paper, they’ll remember the authors and know not to take their work too seriously in the future. And, in my case, if they see a crappy fellowship application, they’ll toss it out.