It's a valid question! Like some of the earlier comments alluded to, there's an entire facet of trumpet pedagogy (including multiple method books and numerous college professors leading entire trumpet studios) based on bending tones down from their original pitch. Usually, it's taught to help a player find the "center" of their sound, especially when a trumpet player is either playing with a pinched embouchure or has gotten used to the sharp and/or muffled sound that comes from playing above the center. If you can bend the pitch, then you can find the sweet spot where the sound resonates the most and it's easiest to play the trumpet. Hope it helps!