Guidance from agencies can be extremely useful because it often indicates what positions the agencies will take in, for example, litigation under the statute itself, and avoiding litigation usually saves businesses a ton of money. The same with non-regulation guidance from the IRS, which will sometimes contain safe harbors that taxpayers can rely on. Again, that’s a big savings in time and money, particularly if compliance under the statute is onerous and the agency guidance provides shortcuts.
Taking that guidance away in many cases can make things worse, not better, if all that’s left is a broad, ambiguous statute written by Congress.