In the UK there is substantial use of secondary legislation. This is where Parliament authorises someone else to make laws on its behalf in some context. These powers delegated by Parliament are usually mundane but can be extreme and there's no limit to what powers Parliament can delegate. Since politicians are lazy they tend to use secondary legislation all the time. This encourages a culture of legislative sloppiness.
While the UK courts have given themselves the power to perform judicial review, there is no constitutional basis for this review and so the courts are reluctant to step on Parliament's toes because if they go too far they risk Parliament deciding that it doesn't like the courts' interference and removing their authority. This isn't a hypothetical and the courts have at times resorted to some crazy mental gymnastics to evade Parliament's attempts to prevent judicial review.
The US has a similar concept that enables federal agencies to make regulations on Congress's behalf but it's much more limited in scope due to the separation of powers and more solid position of the US Supreme Court.
I believe the analogous concept is Chevron deference here in the US. It must be a relatively easy optimization to make to reduce legislative load considering it arises so often. Interesting.
One funny thing in California that is relevant is lane splitting. It is legal but guidelines are decided on by the CHP (state police). In practice, this means they have discretion to pull you over.
I must imagine this is like the creation of Shadow IT in organizations. In the past, when you made it hard to get a server or whatever, you’d end up with your org building their software somewhere else where IT can’t see it.
This must be the legal innovation that matches that: if law is hard to pass, shove a bunch of things off into Shadow Legislative which can then change rules on a whim.
It’s essentially a mechanism to re-enable rapid decision making in a sclerotic system. So perhaps the US using it less than the Old World is simply an artifact of age (though extant nations vary, the legal traditions of the Old World seem to have endured) and in time we will see it dominate the US as well.