We could, but we don't do enough of it because of liability risks. Imagine if the controlled burn goes out of control, and burns down <someone's lakehouse/dacha/cabin/dog/three month old baby>.

People will be in the streets, crying for blood, and won't give up until the Department of Controlled Forest Burns is dissolved, and its executives are sleeping in the Bay, wearing cement overshoes.

Yes, you can buy insurance for this sort of thing, but no, money doesn't grow on trees, and insuring your controlled burn program is not going to come cheap.