The trouble with rules & regs, especially those driven by pressure groups, is that they never rescind anything. Speed limits only ever go down and, no matter what they are, some loony will still want them lower. Usually because they don't understand that sometimes sh*t happens: "Oh no, an accident on a 20mph road. It's obviously too fast, make it 10."
In the same vein, and you can throw the alcohol/driving limits in with this, they don't understand that it's irrelevant what the law is when the only remaining problems they're trying to stop are the people hitting the scenery at Mach 2 with a bottle of scotch in them.
It becomes counter productive in the end, hence people with 30 years of clean licenses who bimble to the shops happily, start collecting points as if there's a set of crystal tumblers at the end of it. When they start insisting everyone has cameras watching that the driver doesn't salivate at the thought of a Twix, let alone actually eating one, we'll all have 300 points and insurance through the roof. And still for no benefit as the people who think two insurance claims a year is perfectly normal won't realise they were the target.
I go to the land of the dragon regularly and some of the 20s are on roads so wide that the nearest accident is 15 seconds away.
Back to wherever I started; it's like VED, trailer towing licensing[1], van speed limits[2], they tinker with things making it eternally worse and utterly incomprehensible without having a clear out and tidy up. So the limits will probably stay.
[1] They didn't half botch those
[2] Modern vans still seem to be viewed through the 1956 lens of something with a 1t payload being a lorry that needed Popeye at the controls.