Actually you are incorrect here, and as a poker player I would think you'd know better. To sum up:
Horse Racing: House takes X% of the betting pool, then leaves it to the bettors.
Poker: House takes X% of the betting pool, then...you see.
Just as you find poker players who are just 'goofing around' or don't really understand pot odds and other factors, so you find horseplayers who bet on a horse who looks pretty, or a jockey with the same name as a relative, etc. Same thing, you are capitalizing on mistakes made by your competition to derive a long-term profit.
Perhaps a simple way to explain the difference is, in horse racing the cards are all face up, and you can only bet before the community cards are dealt.
