>>47506598Grimer, Gastly are the result of human pollution.
Voltorb and Magnemite of human abusing electricity.
Mewtwo as mankinds possibly destroying itself by trying to clone/control God ( Mew )
LT Surge by explaining Pokemon were used as tools/guns in war.
And remember how Bill got turned into a Pokemon by messing with the PC? Thats a hint on how trade-evo used to work.
Between the trade the two Pokemon get their Data corrupted/mixed, resulting in the final forms that dont resemble the previous one and cant be found in the wild.
Besides Pic related, Alakazam for instance looks weak, loses his tail and gets stronger, while Gengar by sucking his vitality gets a form and stop being made outta gas like its previous forms.
This concept is even continued in Gen 2. Scyther/Onix get their DNA mixed with the Metal Coat they hold while being traded.
Obviously this is a bit dark so they kinda dropped this theme.