why is it that some train sets have deisel engines but carry passenger & mail. that gives a 45% bonus & if passenger wagons are in set with electric engines you will get 100% bonus right? i thought cargo went with deisel engines & passenger & mail went with electric engines in order to get the best bonus. i'm confused..easily. lol.
King of the Race is not the only electric cargo set in the game.
Another answer to the question in the OP is: Because it shows that there's a time and a place for everything. Even if the bonuses need to be adjusted to keep the game balanced, it's appropriate for Pixel to give us a diesel passenger set and an electric cargo set occasionally.
Some would argue that they're not only appropriate, but also necessary. After all, those things exist with real trains. Why shouldn't they exist in one of the best train games ever made?