If you build a deck with sideboarding in mind, even with a 5 card sideboard you could easily tech in pokemon to destroy any matchup.
I will give a few examples.
So lets say your deck has a bad match-up against 6-corners. You then side-board in something like 3-4 Lost removers. The deck plays a ton of special NRG, and There is no way to counter the maxed out Lost Remover count. The deck has to hit its energy drops consistently, and if you have all the lost removers you need. You'lll swing the match heavily in your favor.
Someone already posted that you swing any lightning match up in your favor with adding four Terrakion. And if you have a bad matchup against lightning you can build you deck in such a way that you will already be able to meet the fighting NRG requirement. How do you counter side-board against Terrakion? 4 Tornadus? some DCE?
Pokemon is a VERY different game from magic and yugioh. Its pretty easy to find a hard counter to your opponents pokemon, so sideboarding doesn't really take much skill for pokemon. It just takes maxing out your count of some hard counter like Tornadus, Mewtwo, Absol, Terrakion, Cobalion, etc.
My last example is the big basic decks like Electrode+anything or 6-corners. These decks (once again) can just sideboard in a maxed-out counter to whatever the opponent is running (or take electrode out or put it back in).
Sideboarding in pokemon would be pretty mindless is most cases. Whereas, getting a 60 card deck to be consistent and also including what you need for bad match-ups (and evaluation of your meta, and popular decks to determine if the tech is worth they space) takes a significant amount of skill.
TL;DR:
Because of the way the Pokemon TCG works, sideboarding would be mindless. Building a deck 60 deck with techs that is still consistent takes considerably more skill.
I will give a few examples.
So lets say your deck has a bad match-up against 6-corners. You then side-board in something like 3-4 Lost removers. The deck plays a ton of special NRG, and There is no way to counter the maxed out Lost Remover count. The deck has to hit its energy drops consistently, and if you have all the lost removers you need. You'lll swing the match heavily in your favor.
Someone already posted that you swing any lightning match up in your favor with adding four Terrakion. And if you have a bad matchup against lightning you can build you deck in such a way that you will already be able to meet the fighting NRG requirement. How do you counter side-board against Terrakion? 4 Tornadus? some DCE?
Pokemon is a VERY different game from magic and yugioh. Its pretty easy to find a hard counter to your opponents pokemon, so sideboarding doesn't really take much skill for pokemon. It just takes maxing out your count of some hard counter like Tornadus, Mewtwo, Absol, Terrakion, Cobalion, etc.
My last example is the big basic decks like Electrode+anything or 6-corners. These decks (once again) can just sideboard in a maxed-out counter to whatever the opponent is running (or take electrode out or put it back in).
Sideboarding in pokemon would be pretty mindless is most cases. Whereas, getting a 60 card deck to be consistent and also including what you need for bad match-ups (and evaluation of your meta, and popular decks to determine if the tech is worth they space) takes a significant amount of skill.
TL;DR:
Because of the way the Pokemon TCG works, sideboarding would be mindless. Building a deck 60 deck with techs that is still consistent takes considerably more skill.