>>43189833The games flat out encourage experimenting, replacing and using more than just a static team of 6. From mon BSTs making earlygame mons with investment outclassed by a later, freshly caught one, in-game trades being convenient ways to get past certain challenges (Hoenn's Makuhita trade and Johto's female Machop before Roxanne and Whitney, respectively), rewards for catching Pokemon (Kanto's assistant and Alola's mini-sidequests), to some NPCs flat out telling you that you should give certain Pokemon a shot (the Roughneck who beat Roxie using a Magnemite).
The games were made to try out something new instead of using the same thing over and over.