Sure, for each individual case they can learn some rule or exception for that specific word. But it takes some time to learn them all. "Check whether what you just read makes sense in context" is a general rule that can be applied to discover mistakes.

I wasn't suggesting that "house" vs "horse" is a particularly difficult distinction, but rather that just looking at the letters is not enough. Kids really do need those additional rules, and until they've learned them, some kind of error correction is necessary.