I mean, have you
looked at the mathematical mechanics of the game? The Pokeball
catch rate calculation involves horrific equations like:
a = (3 × HPmax - 2 × HPcurrent) × (rate × bonusball) / (3 × HPmax) + bonusstatus
and
Catch = 1048560 / √(√(16711680 / CatchValue)) = (220 - 24) / √(√((224 - 216) / CatchValue))
with some poor soul at the Pokemon game company crying over the fact these equations will probably change with each subsequent generation with the introduction of new kinds of Pokeballs with different catch rates and modifiers that depend on the type/gender of the Pokemon and time of day. And you know, catch rate is nothing compared to the implementation of stat systems and how they coincide with natures and the EV/IV combinations, STAB and whatnot, etc.
The creators of the Pokemon games didn't go through months/years of angry tears towards mathematical equations and coding and all-nighters just so their game could be played by 10 year old's with no regard to this amount of effort. >=[
(I actually don't know what I'm talking about)
Point being, if it were solely made for kids, it wouldn't make sense to put in all these additional complications. It's audience is meant to branch out to people above the age of 10.
There's also a whole Competitive Battling community that uses these complex stat systems and type advantages/disadvantages and move speed priorities and item mechanics to enhance the battle system. The game was designed to allow for this potential type of battling - the game becomes not just a story-telling thing with cool fighting animals that can use cool attacks, but another medium of serious gaming that relies on understanding the complicated mechanics that children* probably wouldn't bother with or easily understand. It goes from playing to gaming.