If the incline press already engages the entire chest and all pressing movements work the front deltoids, why do people still perform the flat press and the overhead press?

I've been wondering about the necessity of including flat press and overhead press if the incline press already works the entire chest and all pressing movements naturally engage the front delts. Is there a specific benefit to these exercises that incline pressing alone doesn't provide? Or is it more about variation and targeting muscles from different angles?