Okay, let's see what happens if Satoshi does capture every wild Pokémon he sees, shall we?
- By the end of the Kanto region, he has well over 100 Pokémon, but he barely gets to use them at all because he's constantly swapping them around (and if he didn't, he'd never use some of them and he would have caught them for no reason)
- None of his Pokémon ever get any decent screen time or character development because there are so dang many of them
- Add to this the Jouto and Houen regions, and Satoshi has over 300 Pokémon that he's continually trying to swap and transfer in order to give them all equal experience, which negates the attempt in Houen to give the Pokémon real fleshed-out personalities (something that can't be done if the Pokémon only appears in one or two episodes)
Now, that seems pretty stupid, doesn't it?