Why isn't resistance a case of halving any damage taken?

Question

In the Pokémon TCG, there is something called Resistance and Weakness. Like this:

For example, for some games, you have multipliers like 1x for 'Neutral Attacks' that aren't affected by Resistance or Weakness, 2x - or something like that - for 'Effective Attacks'and 0.5x for 'Ineffective attacks'.

But why in the TCG does Weakness cause 2x damage, and Resistance cause -20 damage?

There is an argument to this:

For a new change:

• Low Damage attacks (those <20) will cause no damage, or even help them to heal (if it is possible).
• If the damage is an odd number multiplied by 10 (like 10, 30, 150...), it would cause it to do damage like 5, 25, 75, 165 and damage like that. But this can be resolved by introducing a '5' Damage Counter, and that can be counted as 1/2 a damage counter.

Against a new change:

• It has already been like this for a while.

Obviously, there are more arguments, but these few will provide enough justification, I believe.

So why was -20 introduced, not ÷2?

I am looking for:

• Why they didn't do it like the mainline Pokemon games?

Answer 1

My uninformed, best guess:

The Pokémon card game was designed to be simple and playable by young children. Subtracting 20 is a simple operation, as is multiplication by small numbers, but division is more complicated, can lead to mistakes, and requires instructions on how to round "half" values (or 5s, in this case) up or down.