Most games I've seen, nobody ever horse trades for color groups.

Complex deals and negotiations, land swaps, leveraged buyouts, and free rent passes, are all supposed to be part of the game. Getting a color group solely by landing on the spaces first and buying them for list price is indeed rare, by design.

This leads to my other pet peeve... You're not supposed to have enough money to go around the board the first time and buy every space you land on at the list price. You're supposed to be forced to make strategic decisions from the beginning of the game about what you go for, and what you bid in the auctions.

Most of the made up "house rules" are really about circulating more money into the game than is supposed to be there.